Method and system for providing a return path for signals generated by legacy terminals in an optical network

ABSTRACT

A return path system includes inserting RF packets between regular upstream data packets, where the data packets are generated by communication devices such as a computer or internet telephone. The RF packets can be derived from analog RF signals that are produced by legacy video service terminals. In this way, the present invention can provide an RF return path for legacy terminals that shares a return path for regular data packets in an optical network architecture. The invention operates independently of a legacy upstream transmission timing scheme so that the legacy upstream transmission timing scheme can remain effective in preventing data collisions. In other embodiments, the present invention allows for less complex hardware for subscribers that are not taking data services. Further, an optical signal present line in combination with a driver may be employed in order to reduce the amount of hardware in a laser transceiver node.

STATEMENT REGARDING RELATED APPLICATIONS

The present application is a continuation-in-part of non-provisionalpatent application entitled, “System and Method for CommunicatingOptical Signals Between A Data Service Provider and Subscribers,” filedon Jul. 5, 2001 and assigned U.S. application Ser. No. 09/899,410; andthe present application claims priority to provisional patentapplication entitled, “Method and Apparatus for Returning RF Signalsfrom Subscribers to the Headend,” filed on Aug. 3, 2001 and assignedU.S. application Ser. No. 60/309,484.

TECHNICAL FIELD

The present invention relates to video, voice, and data communications.More particularly, the present invention relates to a fiber-to-the-home(FTTH) system that is capable of propagating RF terminal signals from asubscriber to a data service provider.

BACKGROUND OF THE INVENTION

The increasing reliance on communication networks to transmit morecomplex data, such as voice and video traffic, is causing a very highdemand for bandwidth. To resolve this demand for bandwidth,communications networks are relying upon optical fiber to transmit thiscomplex data. Conventional communication architectures that employcoaxial cables are slowly being replaced with communication networksthat comprise only fiber optic cables. One advantage that optical fibershave over coaxial cables is that a much greater amount of informationcan be carried on an optical fiber.

While the FTTH optical network architecture has been a dream of manydata service providers because of the aforementioned capacity of opticalfibers, implementing the FTTH optical network architecture may encountersome problems associated with legacy systems that are in current use bysubscribers. For example, many subscribers of data service providers useset top terminals (STTs) to receive and transmit information related tovideo services. The conventional set top terminals are coupled to acoaxial cable. The coaxial cable, in turn, is then connected to fiberoptic cables in a hybrid fiber-coax (HFC) system. The coaxial cable fromthe set top terminals in combination with the fiber optic cables providea two way communication path between the set top terminal and the dataservice hub for purposes such as authorizing a subscriber to viewcertain programs and channels.

For example, conventional set top terminals coupled to coaxial cablesmay provide impulse pay-per-view services. Impulse pay-per-view servicestypically require two way communications between the set top terminaland the data service provider. Another exemplary service that mayrequire two-way communication passed between the set top terminal andthe data service provider is video-on-demand (VOD) services.

For video on demand services, a subscriber can request a program of hischoosing to be played at a selected time from a central video fileserver at the data service hub. The subscriber's VOD program request istransmitted upstream on a return channel that comprises coaxial cablescoupled to fiber optic cables. With the VOD service, a subscribertypically expects VCR-like control for these programs which includes theability to “stop” and “play” the selected program as well as “rewind”and “fast forward” the program.

In conventional HFC systems, a return RF path from the subscriber to thedata service hub is provided. The RF return path is needed because aconventional set top terminal usually modulates its video serviceupstream data onto an analog RF carrier. While the video serviceupstream data may be modulated onto an RF carrier, it is recognized thatthe upstream data may be in digital form.

An RF return path typically comprises two-way RF distribution amplifierswith coaxial cables and two-way fiber optic nodes being used tointerface with fiber optic cables. A pair of fiber optic strands can beused to carry the radio frequency signals between the head end and nodein an analog optical format. Each optical cable of the pair of fiberoptic strands carries analog RF signals: one carries analog RF signalsin the downstream direction (toward the subscriber) while the otherfiber optic cable carries analog RF signals in the reverse or upstreamdirection (from the subscriber). In a more recent embodiment, theupstream spectrum (typically 5–42 MHz in North America) is digitized atthe node. The digital signals are transmitted to the headend, where theyare converted back to the analog RF spectrum of 5–42 MHz. This processtypically uses high data rates (at least 1.25 Gb/s) and a fiber orwavelength dedicated to return traffic from one or two nodes.

Unlike HFC systems, conventional FTTH systems typically do not comprisea return RF path from the subscriber to the data service hub becausemost of the return paths comprise only fiber optic cables that propagatedigital data signals as opposed to analog RF signals. In conventionalFTTH systems, a downstream RF path is usually provided because it isneeded for the delivery of television programs that use conventionalbroadcast signals. This downstream RF path can support RF modulatedanalog and digital signals as well as RF modulated control signals forany set top terminals that may be used by the subscriber. However, asnoted above, conventional FTTH systems do not provide for any capabilityof supporting a return RF path for RF analog signals generated by thelegacy set top terminal.

Accordingly, there is a need in the art for the system and method forcommunicating optical signals between a data service provider and asubscriber that eliminates the use of the coaxial cables and the relatedhardware and software necessary to support the data signals propagatingalong the coaxial cables. There is also a need in the art for a systemand method that provides a return path for RF signals that are generatedby legacy video service terminals. An additional need exists in the artfor a method and system for propagating upstream RF packets with verylow latency and jitter. A further need exists in the art for a method insystem for communicating optical signals between a data service providerand a subscriber that preserves the upstream transmission timing schemethat is controlled by a legacy video service controller. Another needexists in the art for supporting legacy video service controllers andterminals with an all optical network architecture.

SUMMARY OF THE INVENTION

The present invention is generally drawn to a system and method forefficient propagation of data and broadcast signals over an opticalfiber network. More specifically, the present invention is generallydrawn to an optical network architecture that can provide a return pathfor RF signals that are generated by existing legacy video serviceterminals. Video service terminals can comprise set top terminals orother like communication devices that may employ RF carriers to transmitupstream information.

In one exemplary embodiment, a portion of the return path may be housedin a subscriber optical interface. The subscriber optical interface maycomprise an analog to digital converter where analog RF electricalsignals produced by a video service terminal are converted to digitalelectrical signals.

The return path in the subscriber optical interface may further comprisea data reducer that shortens or reduces the size of the digitized RFelectrical signals. A data conditioner can be coupled to the datareducer for generating identification information as well as timinginformation that are linked to the digitized and reduced RF signals toform RF packets. That is, an RF packet can comprise digitized andreduced RF signals that are coupled with identification and timinginformation. The timing information, also referred to as a time stamp,processed by the data conditioner is one important feature of theinvention that is used later in a data service hub to reconstruct theanalog RF electrical signals as will be discussed below.

The data conditioner may further comprise a buffer such as a FIFO forspeeding up the transmission rate of the RF packets. This increase intransmission rate of the RF packets is another important feature of thepresent invention. A switch connected to the data conditioner andprocessor can be controlled by the processor of the subscriber opticalinterface. The switch may be activated at appropriate times to combinethe RF packets with data signals destined for a data service hub.

More specifically, the RF packets may be inserted between upstreampackets comprising data generated by a subscriber with a communicationdevice such as a computer or internet telephone. The term “upstream” candefine a communication direction where a subscriber originates a datasignal that is sent upwards towards a data service hub of an opticalnetwork. Conversely, the term “downstream” can define a communicationdirection where a data service hub originates a data signal that is sentdownwards towards subscribers of an optical network.

This insertion of RF packets between data packets for upstreamtransmission is yet another important feature of the invention. In otherwords, the timing at which the RF packets are inserted between upstreamdata packets for upstream transmission is one inventive aspect of thepresent invention. The amount of time between RF packet transmissions istypically smaller than the amount of time allotted for the production ofthe analog RF signal produced by the video service terminal.

Stated differently, the size of the RF signal produced by the videoservice terminal as measured in time is usually greater than the amountof time between upstream transmission of the RF packets. While theupstream transmission of data packets can be interrupted at intervalswith upstream RF packet transmission, it is noted that the intervals ofinterruption do not need to be regularly spaced from one another intime. However, in one embodiment, the interruptions can be designed tobe spaced at regular, uniform intervals from one another. In anotherexemplary embodiment, the interruptions could be spaced at irregular,non-uniform intervals from one another. With the present invention, theupstream transmission of RF packets can occur with very low latency andjitter.

Another unique feature of the present invention is that the timingbetween legacy video service terminal transmissions is typically notcontrolled by the present invention. In other words, the presentinvention can preserve the upstream transmission timing scheme that isgenerated by the legacy video service controller that is housed withinthe data service hub. The upstream transmission timing scheme generatedby the legacy video service controller is usually designed to eliminateany collisions between RF signals produced by different video serviceterminals. The present invention can operate independently of thislegacy upstream transmission timing scheme so that the legacy upstreamtransmission timing scheme can remain effective.

Another portion of the RF return path may be disposed in a transceivernode coupled to the subscriber optical interface. The transceiver nodemay comprise an optical tap routing device that can separate the RFpackets from the data packets. Another data conditioner comprising abuffer such as a FIFO may be coupled to the optical tap routing devicein order to slow down the transmission rate of the RE packets. Thedecrease in the transmission rate of the RF packets is another inventivefeature of the present invention. The RF packets leaving the dataconditioner may be converted to the optical domain with an opticaltransmitter. Since the RF packets leaving the conditioner have a slowertransmission rate, low power and inexpensive optical transmitters can beused. The optical transmitter may propagate the RF packets towards thedata service hub along an optical waveguide that can also carrydownstream video signals and video service control signals.

A data service hub may comprise another portion of the RF return path.This portion of the RF return path may comprise a diplexer thatseparates downstream video and video service control signals fromupstream RF packets. The RF packet can then be converted back to theelectrical domain with an optical receiver. The upstream RF packets maybe processed by a delay generator that plays back the upstream RFpackets with a predetermined delay that corresponds with the time stampof the RF packet. The RF packet may then be expanded with a data to RFconverter that transforms the RF packet back to its original analog RFsignal format. An RF receiver coupled to a video service controller maythen process the restored analog RF signals.

In another alternate exemplary embodiment, some subscribers may not betaking data services while other subscribers are taking data services.In this embodiment, a simple analog optical transmitter can be providedin the subscriber optical interface for the subscribers not taking dataservices while the hardware for forming the RF data packets from thesubscribers not receiving data can be housed in the transceiver node.

In a further exemplary embodiment, all subscribers may not be receivingor transmitting any data. In this exemplary embodiment, a simple analogoptical transmitter can be provided in each subscriber optical interfacewhile the hardware for forming the RF data packets is housed in thetransceiver node. Also, all hardware associated with handling data inthe transceiver node can be eliminated.

In an additional exemplary embodiment where all of the subscribers maynot be receiving or transmitting any data, a simple analog opticaltransmitter can be provided in the subscriber optical interface whilethe laser transceiver node is designed to propagate analog opticalsignals back to the data service hub.

In another alternative exemplary embodiment, an optical signal presentline in combination with a driver may be employed in order to reduce theamount of hardware in a node. Specifically, the optical signal presentline may permit two or more optical receivers to be serviced by a signalmultiplexer. In such an embodiment, the optical signal present line canalso function to detect a new terminal as it is added to the opticalnetwork.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of some core components of anexemplary optical network architecture according to the presentconvention that can support legacy video services.

FIG. 2 is a functional block diagram illustrating additional aspects ofan exemplary optical network architecture according to the presentinvention.

FIG. 3 is a functional block diagram illustrating an exemplary dataservice hub of the present invention.

FIG. 4 is a functional block diagram illustrating an exemplary dataservice hub of the present invention that is designed to supportmultiple transceiver nodes.

FIG. 5 is a functional block diagram illustrating an exemplarytransceiver node according to the present invention.

FIG. 6 is a functional block diagram illustrating an alternate exemplaryembodiment of transceiver node according to the present invention wheremultiple laser optical receivers share an optical tab multiplexer.

FIG. 7 is a functional block diagram illustrating another transceivernode according to the present invention where the transceiver nodecomprises a plurality of tap multiplexers and associated upstream datatransmissions.

FIG. 8 is a functional block diagram illustrating an optical tapconnected to a subscriber optical interface by a signal wave guideaccording to one exemplary embodiment of the present invention.

FIG. 9 is a functional block diagram illustrating an overview of severalof the main components according to one exemplary embodiment of thepresent invention.

FIG. 10 a is a functional block diagram illustrating some corecomponents of a data reducer.

FIG. 10 b is a graph illustrating an exemplary Nyquist sampling spectrumof an RF return signal according to one exemplary embodiment of thepresent invention.

FIG. 10 c is a graph illustrating an exemplary digitized RF signal thatis multiplied by a number representing a sinusoidal waveform.

FIG. 10 d is a logic flow diagram illustrating an exemplary method forscaling data received from a video service terminal that can beperformed by a data scaling unit illustrated in FIG. 10 a.

FIG. 11 a is a functional block diagram that describes further detailsof a data-to-RF converter.

FIG. 11 b illustrates an exemplary scaling restoration process accordingto one exemplary embodiment of the present invention.

FIG. 12 illustrates an exemplary computation of a burst process for anexemplary embodiment of the present invention.

FIG. 13 illustrating an exemplary length of a data burst according toone exemplary embodiment of the present invention.

FIG. 14 is a diagram illustrating the timing of some exemplary RF returntransmissions and some exemplary rules for handling RF packets.

FIG. 15 illustrates exemplary timing delays that can occur betweenrespective subscriber optical interfaces and laser transceiver nodesaccording to the present invention.

FIG. 16 is a diagram illustrating an exemplary embodiment where each ofthe legacy video service terminals are unmarshaled, meaning that thevideo service terminals do not know how much in advance of the start ofa video service time slot they are to transmit to make up for anypropagation delays.

FIG. 17 is a diagram illustrating an exemplary embodiment where eachlegacy video service terminal is marshaled, meaning that each legacyvideo service terminal does know how much in advance of the start of anupstream transmission time slot they are to transmit to make up for anypropagation delays.

FIG. 18 illustrates an alternative and exemplary embodiment in which asubscriber is not subscribing to any data services while data servicesare being supplied to other subscribers.

FIG. 19 illustrates another alternative and exemplary embodiment inwhich data services are not supplied to any subscribers.

FIG. 20 is a diagram illustrating an alternative and exemplaryembodiment in which all subscribers do not receive any data services andin which all RF return signals are propagated by analog lasermodulation.

FIG. 21 is a logic flow diagram illustrating an exemplary method fordeciding which return method to use based upon how subscribers are to beserviced.

FIG. 22 is a logic flow diagram illustrating an exemplary method forpropagating upstream RF signals towards a data service hub.

FIG. 23 is a logic flow diagram illustrating an exemplary subprocess ofcombining reduced RF packets with regular data packets of a routine inFIG. 22.

FIG. 24 is a logic flow diagram illustrating the exemplary processing ofdownstream video service control signals according to an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention may be embodied in hardware or software or acombination thereof disposed within an optical network. In one exemplaryembodiment, the present invention provides a method for inserting RFpackets between upstream packets comprising data generated by asubscriber with a communication device such as a computer or internettelephone. In this way, the present invention can provide an RF returnpath for legacy video service terminals that shares a return path forregular data packets in an optical network architecture. Video serviceterminals can comprise set top terminals or other like communicationdevices that may employ RF carriers to transmit upstream information.

The present invention also provides a way in which the upstreamtransmission timing scheme that is controlled by the legacy videoservice controller housed within the data service hub is preserved. Theupstream transmission timing scheme generated by the legacy videoservice controller is usually designed to eliminate any collisionsbetween RF signals produced by different video service terminals. Thepresent invention can operate independently of this legacy upstreamtransmission timing scheme so that the legacy upstream transmissiontiming scheme can remain effective. The present invention can alsoadjust the transmission rate of RF packets during certain stages in anoptical network in order to take advantage of lower cost hardware.

In an alternate exemplary embodiment, the present invention allows forless complex hardware that can be provided in the subscriber opticalinterface or laser transceiver node or both for subscribers that are nottaking data services.

In other alternative exemplary embodiments, an optical signal presentline in combination with a driver may be employed in order to reduce theamount of hardware in a laser transceiver node. In such an embodiment,the optical signal present line can also function to detect a newterminal as it is added to the optical network.

Referring now to the drawings, in which like numerals represent likeelements throughout the several Figures, aspects of the presentinvention and the illustrative operating environment will be described.

FIG. 1 is a functional block diagram illustrating an exemplary opticalnetwork architecture 100 according to the present invention. Theexemplary optical network architecture 100 comprises a data service hub110 that houses a legacy video services controller 115. The legacy videoservices controller 115 is typically designed to transmit and receivedigital radio-frequency (RF) signals. The legacy video servicescontroller 115 can comprise conventional hardware that supports servicessuch as impulse-pay-per-view and video-on-demand. However, the videoservices controller 115 is not limited to the aforementionedapplications and can include other applications that are not beyond thescope and spirit of the present invention. In some exemplaryembodiments, the video services controller can be split between twolocations. For example, a portion, primarily a computer, can be locatedin a first data service hub 110 that services a plurality of second dataservice hubs 110, while an RF transmitter plus one or more receivers canbe located in each second data service hub 110. The first and pluralityof second data service hubs 110 can be linked using any of several knowncommunications paths and protocols.

The data service hub 110 is connected to a plurality of outdoor lasertransceiver nodes 120. The laser transceiver nodes 120, in turn, areeach connected to a plurality of optical taps 130. The optical taps 130can be connected to a plurality of subscriber optical interfaces 140.Connected to each subscriber optical interface 140 can be video servicesterminal (VST) 117. The video services RF terminal 117 is designed towork with the video services controller 115. The video services RFterminal 117 can receive control signals from the video servicescontroller 115 and can transmit RF-modulated digital signals back to thevideo services controller 115. The RF-modulated digital signals maycomprise the options selected by a user. However, the signals producedby the video service terminal 117 could be analog in form and thenmodulated onto the RF carrier. But most legacy video service terminals117 as of the writing of this description produce digital signals thatare modulated onto an analog RF carrier.

The video services terminal 117 can permit a subscriber to selectoptions that are part of various exemplary video services such asimpulse-pay-per-view and video-on-demand. However, as noted above withrespect to the video services controller 115, the present invention isnot limited to the aforementioned applications and can include numerousother applications where RF analog signals are used to carry informationback to the video services controller 115.

Between respective components of the exemplary optical networkarchitecture 100 are optical waveguides such as optical waveguides 150,160, 170, and 180. The optical waveguides 150–180 are illustrated byarrows where the arrowheads of the arrows illustrate exemplarydirections of data flow between respective components of theillustrative and exemplary optical network architecture 100. While onlyan individual laser transceiver node 120, an individual optical tap 130,and an individual subscriber optical interface 140 are illustrated inFIG. 1, as will become apparent from FIG. 2 and its correspondingdescription, a plurality of laser transceiver nodes 120, optical taps130, and subscriber optical interfaces 140 can be employed withoutdeparting from the scope and spirit of the present invention. Typically,in many of the exemplary embodiments of the RF return system of thepresent invention, multiple subscriber optical interfaces 140 areconnected to one or more optical taps 130.

The outdoor laser transceiver node 120 can allocate additional orreduced bandwidth based upon the demand of one or more subscribers thatuse the subscriber optical interfaces 140. The outdoor laser transceivernode 120 can be designed to withstand outdoor environmental conditionsand can be designed to hang on a strand or fit in a pedestal or “handhole.” The outdoor laser transceiver node can operate in a temperaturerange between minus 40 degrees Celsius to plus 60 degrees Celsius. Thelaser transceiver node 120 can operate in this temperature range byusing passive cooling devices that do not consume power.

Unlike the conventional routers disposed between the subscriber opticalinterface 140 and data service hub 110, the outdoor laser transceivernode 120 does not require active cooling and heating devices thatcontrol the temperature surrounding the laser transceiver node 120. TheRF system of the present invention attempts to place more of thedecision-making electronics at the data service hub 110 instead of thelaser transceiver node 120. Typically, the decision-making electronicsare larger in size and produce more heat than the electronics placed inthe laser transceiver node of the present invention. Because the lasertransceiver node 120 does not require active temperature controllingdevices, the laser transceiver node 120 lends itself to a compactelectronic packaging volume that is typically smaller than theenvironmental enclosures of conventional routers. Further details of thecomponents that make up the laser transceiver node 120 will be discussedin further detail below with respect to FIGS. 5, 6, and 7.

In one exemplary embodiment of the present invention, three trunkoptical waveguides 160, 170, and 180 (that can comprise optical fibers)can propagate optical signals from the data service hub 110 to theoutdoor laser transceiver node 120. It is noted that the term “opticalwaveguide” used in the present application can apply to optical fibers,planar light guide circuits, and fiber optic pigtails and other likeoptical waveguide components that are used to form an opticalarchitecture.

A first optical waveguide 160 can carry downstream broadcast video andcontrol signals generated by the video services controller 115. Thesignals can be carried in a traditional cable television format whereinthe broadcast signals are modulated onto carriers, which in turn,modulate an optical transmitter (not shown in this Figure) in the dataservice hub 110. The first optical waveguide 160 can also carry upstreamRF signals that are generated by respective video service terminals 117.Further details of the format of the upstream RF signals will bediscussed below.

A second optical waveguide 170 can carry downstream targeted servicessuch as data and telephone services to be delivered to one or moresubscriber optical interfaces 140. In addition to carryingsubscriber-specific optical signals, the second optical waveguide 170can also propagate internet protocol broadcast packets, as is understoodby those skilled in the art.

In one exemplary embodiment, a third optical waveguide 180 can transportdata signals upstream from the outdoor laser transceiver node 120 to thedata service hub 110. The optical signals propagated along the thirdoptical waveguide 180 can also comprise data and telephone servicesreceived from one or more subscribers. Similar to the second opticalwaveguide 170, the third optical waveguide 180 can also carry IPbroadcast packets, as is understood by those skilled in the art.

The third or upstream optical waveguide 180 is illustrated with dashedlines to indicate that it is merely an option or part of one exemplaryembodiment according to the present invention. In other words, the thirdoptical waveguide 180 can be removed. In another exemplary embodiment,the second optical waveguide 170 propagates optical signals in both theupstream and downstream directions as is illustrated by the doublearrows depicting the second optical waveguide 170.

In such an exemplary embodiment where the second optical waveguide 170propagates bidirectional optical signals, only two optical waveguides160, 170 would be needed to support the optical signals propagatingbetween the data server's hub 110 in the outdoor laser transceiver node120. In another exemplary embodiment (not shown), a single opticalwaveguide can be the only link between the data service hub 110 and thelaser transceiver node 120. In such a single optical waveguideembodiment, three different wavelengths can be used for the upstream anddownstream signals. Alternatively, bi-directional data could bemodulated on one wavelength.

In one exemplary embodiment, the optical tap 130 can comprise an 8-wayoptical splitter. This means that the optical tap 130 comprising an8-way optical splitter can divide downstream optical signals eight waysto serve eight different subscriber optical interfaces 140. In theupstream direction, the optical tap 130 can combine the optical signalsreceived from the eight subscriber optical interfaces 140.

In another exemplary embodiment, the optical tap 130 can comprise a4-way splitter to service four subscriber optical interfaces 140. Yet inanother exemplary embodiment, the optical tap 130 can further comprise a4-way splitter that is also a pass-through tap meaning that a portion ofthe optical signal received at the optical tap 130 can be extracted toserve the 4-way splitter contained therein while the remaining opticalenergy is propagated further downstream to another optical tap oranother subscriber optical interface 140. The present invention is notlimited to 4-way and 8-way optical splitters. Other optical taps havingfewer or more than 4-way or 8-way splits are not beyond the scope of thepresent invention.

Referring now to FIG. 2, this Figure is a functional block diagramillustrating an exemplary optical network architecture 100 that furtherincludes subscriber groupings 200 that correspond with a respectiveoutdoor laser transceiver node 120. FIG. 2 illustrates the diversity ofthe exemplary optical network architecture 100 where a number of opticalwaveguides 150 connected between the outdoor laser transceiver node 120and the optical taps 130 is minimized. FIG. 2 also illustrates thediversity of subscriber groupings 200 that can be achieved with theoptical tap 130.

Each optical tap 130 can comprise an optical splitter. The optical tap130 allows multiple subscriber optical interfaces 140 to be coupled to asingle optical waveguide 150 that is connected to the outdoor lasertransceiver node 120. In one exemplary embodiment, six optical fibers150 are designed to be connected to the outdoor laser transceiver node120. Through the use of the optical taps 130, sixteen subscribers can beassigned to each of the six optical fibers 150 that are connected to theoutdoor laser transceiver node 120.

In another exemplary embodiment, twelve optical fibers 150 can beconnected to the outdoor laser transceiver node 120 while eightsubscriber optical interfaces 140 are assigned to each of the twelveoptical fibers 150. Those skilled in the art will appreciate that thenumber of subscriber optical interfaces 140 assigned to a particularwaveguide 150 that is connected between the outdoor laser transceivernode 120 and a subscriber optical interface 140 (by way of the opticaltap 130) can be varied or changed without departing from the scope andspirit of the present invention. Further, those skilled in the artrecognize that the actual number of subscriber optical interfaces 140assigned to the particular fiber optic cable is dependent upon theamount of power available on a particular optical fiber 150.

As depicted in subscriber grouping 200, many configurations forsupplying communication services to subscribers are possible. Forexample, while optical tap 130 _(A) can connect subscriber opticalinterfaces 140 _(A1) through subscriber optical interface 140 _(AN) tothe outdoor laser transmitter node 120, optical tap 130 _(A) can alsoconnect other optical taps 130 such as optical tap 130 _(AN) to thelaser transceiver node 120. The combinations of optical taps 130 withother optical taps 130 in addition to combinations of optical taps 130with subscriber optical interfaces 140 are limitless. With the opticaltaps 130, concentrations of distribution optical waveguides 150 at thelaser transceiver node 120 can be reduced. Additionally, the totalamount of fiber needed to service a subscriber grouping 200 can also bereduced.

With the active laser transceiver node 120 of the present invention, thedistance between the laser transceiver node 120 and the data service hub110 can comprise a range between 0 and 80 kilometers. However, thepresent invention is not limited to this range. Those skilled in the artwill appreciate that this range can be expanded by selecting variousoff-the-shelf components that make up several of the devices of thepresent system.

Those skilled in the art will appreciate that other configurations ofthe optical waveguides disposed between the data service hub 110 andoutdoor laser transceiver node 120 are not beyond the scope of thepresent invention. Because of the bi-directional capability of opticalwaveguides, variations in the number and directional flow of the opticalwaveguides disposed between the data service hub 110 and the outdoorlaser transceiver node 120 can be made without departing from the scopeand spirit of the present invention.

Referring now to FIG. 3, this functional block diagram illustrates anexemplary data service hub 110 of the present invention. The exemplarydata service hub 110 illustrated in FIG. 3 is designed for a two trunkoptical waveguide system. That is, this data service hub 110 of FIG. 3is designed to send and receive optical signals to and from the outdoorlaser transceiver node 120 along the first optical waveguide 160 and thesecond optical waveguide 170. With this exemplary embodiment, both thefirst optical waveguide 160 and the second optical waveguide 170 supportbi-directional data flow. In this way, the third optical waveguide 180discussed above is not needed.

The data service hub 110 can comprise one or more modulators 310, 315that are designed to support television broadcast services. The one ormore modulators 310, 315 can be analog or digital type modulators. Inone exemplary embodiment, there can be at least 78 modulators present inthe data service hub 110. Those skilled in the art will appreciate thatthe number of modulators 310, 315 can be varied without departing fromthe scope and spirit of the present invention.

The signals from the modulators 310, 315 are combined in a firstcombiner 320A. The control signals from the video services controller115 are modulated on an RF carrier by an RF transmitter 303. The RFtransmitter 303 feeds its downstream analog RF electrical signals into asecond combiner 320B where the electrical signals from the twomodulators 310, 315 are combined. The combined video services controllersignals and broadcast video signals are supplied to an opticaltransmitter 325 where these signals are converted into optical form.

Those skilled in the art will recognize that a number of variations ofthis signal flow are possible without departing from the scope andspirit of the present invention. For example, the two combiners 320A and320B may actually be one and the same combiner. Also, video signals maybe generated at another data service hub 110 and sent to the dataservice hub 110 of FIG. 3 using any of a plurality of differenttransmission methods known to these skilled in the art. For example,some portion of the video signals may be generated and converted tooptical form at a remote first data service hub 110. At a second dataservice hub 10, they may be combined with other signals generatedlocally.

The optical transmitter 325 can comprise one of Fabry-Perot (F-P) LaserTransmitters, distributed feedback lasers (DFBs), or Vertical CavitySurface Emitting Lasers (VCSELs). However, other types of opticaltransmitters are possible and are not beyond the scope of the presentinvention. With the aforementioned optical transmitters 325, the dataservice hub 110 lends itself to efficient upgrading by usingoff-the-shelf hardware to generate optical signals.

The optical signals generated by the optical transmitter 325 arepropagated to amplifier 330 such as an Erbium Doped Fiber Amplifier(EDFA) where the optical signals are amplified. The amplified opticalsignals are then propagated through a diplexer 420 out of the dataservice hub 110 via a bi-directional video signal input/output port 335which is connected to one or more first optical waveguides 160.

The bi-directional video signal input/output port 335 is connected toone or more first optical waveguides 160 that support bi-directionaloptical signals originating from the data service hub 110 and videoservices terminals 117. The diplexer 420 disposed adjacent to thebi-directional video signal input/output port 335 separates upstreamdigital, optical RF packets originating originated by the video serviceterminals 117 from downstream analog optical RF video service controlsignals and broadcast video signals.

The upstream digital, optical RF packets are fed into an opticalreceiver 370 where the upstream optical RF packets are converted fromthe optical domain into the electrical domain. The optical receiver 370can comprise one or more photoreceptors or photodiodes that convertoptical signals into electrical signals.

Coupled to the optical receiver 370 is a delay generator 305 that cansubstantially reduce or eliminate any latency or jitter in the upstreamRF packets. Further details of the delay generator will be discussedbelow with respect to FIG. 4. The delay generator 305 feeds into adata-to-RF converter 307 that transforms RF packets back into theiroriginal RF analog electrical format. Further details of RF converter307 will be discussed below with respect to FIG. 11. The RF analogelectrical signals generated by the data-to-RF converter 307 aredemodulated by an RF receiver 309. The demodulated signals are thenpropagated to the video services controller 115.

The data service hub 110 illustrated in FIG. 3 can further comprise anInternet router 340. The data service hub 110 can further comprise atelephone switch 345 that supports telephony service to the subscribersof the optical network system 100. However, other telephony service suchas Internet Protocol telephony can be supported by the data service hub110. If only Internet Protocol telephony is supported by the dataservice hub 110, then it is apparent to those skilled in the art thatthe telephone switch 345 could be eliminated in favor of lower cost VoIPequipment. For example, in another exemplary embodiment (not shown), thetelephone switch 345 could be substituted with other telephone interfacedevices such as a soft switch and gateway. But if the telephone switch345 is needed, it may be located remotely from the data service hub 110and can be connected through any of several conventional methods ofinterconnection.

The data service hub 110 can further comprise a logic interface 350 thatis connected to a laser transceiver node routing device 355. The logicinterface 350 can comprise a Voice over Internet Protocol (VoIP) gatewaywhen required to support such a service. The laser transceiver noderouting device 355 can comprise a conventional router that supports aninterface protocol for communicating with one or more laser transceivernodes 120. This interface protocol can comprise one of gigabit or fasterEthernet, Internet Protocol (IP) or SONET protocols. However, thepresent invention is not limited to these protocols. Other protocols canbe used without departing from the scope and spirit of the presentinvention.

The logic interface 350 and laser transceiver node routing device 355can read packet headers originating from the laser transceiver nodes 120and the internet router 340. The logic interface 350 can also translateinterfaces with the telephone switch 345. After reading the packetheaders, the logic interface 350 and laser transceiver node routingdevice 355 can determine where to send the packets of information.

The laser transceiver node routing device 355 can supply downstream datasignals to respective optical transmitters 325. The data signalsconverted by the optical transmitters 325 can then be propagated to abi-directional splitter 360. The optical signals sent from the opticaltransmitter 325 into the bi-directional splitter 360 can then bepropagated towards a bi-directional data input/output port 365 that isconnected to a second optical waveguide 170 that supports bi-directionaloptical data signals between the data service hub 110 and a respectivelaser transceiver node 120.

Upstream optical signals received from a respective laser transceivernode 120 can be fed into the bi-directional data input/output port 365where the optical signals are then forwarded to the bi-directionalsplitter 360. From the bi-directional splitter 360, respective opticalreceivers 370 can convert the upstream optical signals into theelectrical domain. The upstream electrical signals generated byrespective optical receivers 370 are then fed into the laser transceivernode routing device 355. As noted above, each optical receiver 370 cancomprise one or more photoreceptors or photodiodes that convert opticalsignals into electrical signals.

When distances between the data service hub 110 and respective lasertransceiver nodes 120 are modest, the optical transmitters 325 canpropagate optical signals at 1310 nm. But where distances between thedata service hub 110 and the laser transceiver node are more extreme,the optical transmitters 325 can propagate the optical signals atwavelengths of 1550 nm with or without appropriate amplificationdevices.

Those skilled in the art will appreciate that the selection of opticaltransmitters 325 for each circuit may be optimized for the optical pathlengths needed between the data service hub 110 and the outdoor lasertransceiver node 120. Further, those skilled in the art will appreciatethat the wavelengths discussed are practical but are only illustrativein nature. In some scenarios, it may be possible to use communicationwindows at 1310 and 1550 nm in different ways without departing from thescope and spirit of the present invention. Further, the presentinvention is not limited to a 1310 and 1550 nm wavelength regions. Thoseskilled in the art will appreciate that smaller or larger wavelengthsfor the optical signals are not beyond the scope and spirit of thepresent invention.

Referring now to FIG. 4, this Figure illustrates a functional blockdiagram of an exemplary data service hub 110 that provides additionaldetail of hardware that supports multiple upstream RF signalsoriginating from multiple video service terminals 117. The details ofthe hardware handling regular downstream and upstream data is omittedfrom FIG. 4. Only the differences between FIG. 4 and FIG. 3 will bediscussed below.

An electrical splitter 311 is coupled to the video service control RFtransmitter 303. The electrical splitter 311 divides the video servicecontrol signals between combiners 320A, 320B and 320C. Broadcast signalsfrom other combiners 320 are also fed into the aforementioned combiners320A, 320B and 320C.

The electrical splitter 311 can divide the output of the video servicecontrol RF transmitter 303 to provide control signals to a plurality ofoptical nodes 120 and ultimately a plurality of video service terminals117. Each laser transceiver node 120 can serve at least 96 subscribers.

The output of each combiner 320A, 320B and 320C is fed into a respectiveoptical transmitter 325, which in turn, is fed into an optical amplifier330. The signals from each optical amplifier are fed into a respectivediplexer 420. Each diplexer 420 allows a respective optical wave guide160 to propagate bi-directional signals on at least two differentwavelengths. And in one exemplary embodiment, the downstream broadcastand control signals are carried at 1550 nanometers. Upstream RF packetsassociated with the video service terminals 117 can be propagated at1310 nanometers. An optical splitter 415 splits the downstream opticalsignals to serve a number of outdoor laser transceiver nodes 120. Inanother exemplary embodiment (not shown) Diplexer 420 can be omitted,and two fiber strands are used to carry the data in the two directions.

Upstream optical RF packets are combined in the optical splitter 415. Indiplexer 420, the upstream optical RF packets are separated from thedownstream optical signals. The diplexer 420 may comprise a wavedivision multiplexer or other like structures.

From the diplexer 420, the upstream RF data packets are converted intothe electrical domain with an optical receiver 370. The electrical RFdata packets are then forwarded to a respective delay generator 305. Theoutput of each respective delay generator 305 is fed into an adder 313if multiple laser transceiver nodes 120 are being serviced by arespective video service control receiver 309. Specifically, an adder313 enables multiple transceiver nodes to be handled by respectiveindividual data-to-RF converters 307 and video service control receivers309. The adders 313 can reduce the amount of hardware needed by thevideo service controller 115 to manage multiple subscribers.

Referring now to FIG. 5, this Figure illustrates a functional blockdiagram of an exemplary outdoor laser transceiver node 120A of thepresent invention. In this exemplary embodiment, the laser transceivernode 120A can comprise a bi-directional optical signal input port 405that can receive optical signals propagated from the data service hub110 that are propagated along a first optical waveguide 160. The opticalsignals received at the bi-directional optical signal input port 405 cancomprise downstream broadcast video data, downstream video servicecontrol signals, and upstream RF packets.

The downstream optical signals received at the input port 405 arepropagated through a diplexer 420 to an amplifier 410 such as an ErbiumDoped Fiber Amplifier (EDFA) in which the optical signals are amplified.The amplified optical signals are then propagated to an optical splitter415 that divides the downstream broadcast video optical signals andvideo service control signals among diplexers 420 that are designed toforward optical signals to predetermined subscriber groups 200.

The laser transceiver node 120 can further comprise a bi-directionaloptical signal input/output port 425 that connects the laser transceivernode 120 to a second optical waveguide 170 that supports bi-directionaldata flow between the data service hub 110 and laser transceiver node120. Downstream optical signals flow through the bi-directional opticalsignal input/output port 425 to an optical waveguide transceiver 430that converts downstream optical signals into the electrical domain. Theoptical waveguide transceiver further converts upstream electricalsignals into the optical domain. The optical waveguide transceiver 430can comprise an optical/electrical converter and an electrical/opticalconverter.

Downstream and upstream electrical signals are communicated between theoptical waveguide transceiver 430 and an optical tap routing device 435.The optical tap routing device 435 can manage the interface with thedata service hub optical signals and can route or divide or apportionthe data service hub signals according to individual tap multiplexers440 that communicate optical signals with one or more optical taps 130and ultimately one or more subscriber optical interfaces 140. It isnoted that tap multiplexers 440 operate in the electrical domain tomodulate laser transmitters in order to generate optical signals thatare assigned to groups of subscribers coupled to one or more opticaltaps.

Optical tap routing device 435 is notified of available upstream datapackets and upstream RF packets as they arrive, by each tap multiplexer440. The optical tap routing device is connected to each tap multiplexer440 to receive these upstream data and RF packets. The optical taprouting device 435 relays the packets to the data service hub 110 viathe optical waveguide transceiver 430 and bidirectional optical signalinput/output 425. The optical tap routing device 435 can build a lookuptable from these upstream data packets coming to it from all tapmultiplexers 440 (or ports), by reading the source IP address of eachpacket, and associating it with the tap multiplexer 440 through which itcame.

The optical tap routing device 435 can separate upstream data packetsfrom upstream RF packets. The optical tap routing device 435 sendsupstream data packets to the optical waveguide transceiver 430 and RFpackets to a data conditioner 407. The data conditioner 407 can comprisea buffer such as a FIFO. A FIFO is a special purpose circuit known tothose skilled in the art. It takes in data at an interstitial burstrate, then puts out the data (“plays it out”) at the slower clockfrequency that corresponds to the rate at which it was supplied. A FIFOcan begin transmitting data as soon as it begins receiving the data,because it is assured of getting data in data at a fast enough rate thatit will not run out of data before it completes sending the packet.

Therefore, the data conditioner 407 of the laser transceiver node 120can slow down the transmission speed of the upstream RF packets. Forexample, the upstream RF packets may enter the data conditioner 407 at atransmission speed of 500 Megabits per second (Mbps) and exit the dataconditioner at a transmission speed of 40 Megabits per second. However,the present invention is not limited to these exemplary transmissionrates. For example, the exit transmission speed may comprise a rate of25 Megabits per second. But other transmission rates that are faster orslower than those described are not beyond the scope of the presentinvention.

By slowing the transmission speed of the upstream RF packets, the dataconditioner 407 offers several advantages. One advantage is that therelatively slow upstream transmission rate allows the use of lower poweroptical transmitters 325. That is, while optical transmitter 325connected to the data conditioner 407 may comprise one of a Fabry-Perot(F-P) laser, a distributed feedback laser (DFB), or a Vertical CavitySurface Emitting Laser (VCSEL), other lower power lasers can be used.Those skilled in the art recognize that lower power lasers are typicallylower in cost compared to high power lasers. The optical transmitter 325can transmit the upstream RF packets in the 1310 nanometer wavelengthrange.

Referring back to the optical tap routing device 435, the aforementionedlookup table can be used to route packets in the downstream path. Aseach downstream data packet comes in from the optical waveguidetransceiver 430, the optical tap routing device looks at the destinationIP address (which is the same as the source IP address for the upstreampackets). From the lookup table the optical tap routing device 435 candetermine which port (or, tap multiplexer 440) is connected to that IPaddress, so it sends the packet to that port. This can be described as anormal layer 3 router function as is understood by those skilled in theart.

The optical tap routing device 435 can assign multiple subscribers to asingle port. More specifically, the optical tap routing device 435 canservice groups of subscribers with corresponding respective, singleports. The optical taps 130 coupled to respective tap multiplexers 440can supply downstream optical signals to pre-assigned groups ofsubscribers who receive the downstream optical signals with thesubscriber optical interfaces 140.

In other words, the optical tap routing device 435 can determine whichtap multiplexers 440 is to receive a downstream electrical signal, oridentify which tap multiplexer 440 propagated an upstream optical signal(that is received as an electrical signal). The optical tap routingdevice 435 can format data and implement the protocol required to sendand receive data from each individual subscriber connected to arespective optical tap 130. The optical tap routing device 435 cancomprise a computer or a hardwired apparatus that executes a programdefining a protocol for communications with groups of subscribersassigned to individual ports. Exemplary embodiments of programs definingthe protocol is discussed in the following copending and commonlyassigned non-provisional patent applications, the entire contents ofwhich are hereby incorporated by reference: “Method and System forProcessing Downstream Packets of an Optical Network,” filed on Oct. 26,2001 in the name of Stephen A. Thomas et al. and assigned U.S. Ser. No.10/045,652; and “Method and System for Processing Upstream Packets of anOptical Network,” filed on Oct. 26, 2001 in the name of Stephen A.Thomas et al. and assigned U.S. Ser. No. 10/045,584.

The single ports of the optical tap routing device are connected torespective tap multiplexers 440. With the optical tap routing device435, the laser transceiver node 120 can adjust a subscriber's bandwidthon a subscription basis or on an as-needed or demand basis. The lasertransceiver node 120 via the optical tap routing device 435 can offerdata bandwidth to subscribers in pre-assigned increments. For example,the laser transceiver node 120 via the optical tap routing device 435can offer a particular subscriber or groups of subscribers bandwidth inunits of 1, 2, 5, 10, 20, 50, 100, 200, and 450 Megabits per second(Mb/s). Those skilled in the art will appreciate that other subscriberbandwidth units are not beyond the scope of the present invention.

Electrical signals are communicated between the optical tap routingdevice 435 and respective tap multiplexers 440. The tap multiplexers 440propagate optical signals to and from various groupings of subscribersby way of laser optical transmitter 525 and laser optical receiver 370.Each tap multiplexer 440 is connected to a respective opticaltransmitter 325. As noted above, each optical transmitter 325 cancomprise one of a Fabry-Perot (F-P) laser, a distributed feedback laser(DFB), or a Vertical Cavity Surface Emitting Laser (VCSEL). The opticaltransmitters produce the downstream optical signals that are propagatedtowards the subscriber optical interfaces 140. Each tap multiplexer 440is also coupled to an optical receiver 370. Each optical receiver 370,as noted above, can comprise photoreceptors or photodiodes. Since theoptical transmitters 325 and optical receivers 370 can compriseoff-the-shelf hardware to generate and receive respective opticalsignals, the laser transceiver node 120 lends itself to efficientupgrading and maintenance to provide significantly increased data rates.

Each optical transmitter 325 and each optical receiver 370 are connectedto a respective bi-directional splitter 360. Each bi-directionalsplitter 360 in turn is connected to a diplexer 420 which combines theunidirectional optical signals received from the splitter 415 with thedownstream optical signals received from respective optical receivers370. In this way, broadcast video services as well as data services canbe supplied with a single optical waveguide such as a distributionoptical waveguide 150 as illustrated in FIG. 2. In other words, opticalsignals can be coupled from each respective diplexer 420 to a combinedsignal input/output port 445 that is connected to a respectivedistribution optical waveguide 150.

Unlike the conventional art, the laser transceiver node 120 does notemploy a conventional router. The components of the laser transceivernode 120 can be disposed within a compact electronic packaging volume.For example, the laser transceiver node 120 can be designed to hang on astrand or fit in a pedestal similar to conventional cable TV equipmentthat is placed within the “last,” mile or subscriber proximate portionsof a network. It is noted that the term, “last mile,” is a generic termoften used to describe the last portion of an optical network thatconnects to subscribers.

Also because the optical tap routing device 435 is not a conventionalrouter, it does not require active temperature controlling devices tomaintain the operating environment at a specific temperature. Opticaltap routing device 435 does not need active temperature controllingdevices because it can be designed with all temperature-ratedcomponents. In other words, the laser transceiver node 120 can operatein a temperature range between minus 40 degrees Celsius to 60 degreesCelsius in one exemplary embodiment.

While the laser transceiver node 120 does not comprise activetemperature controlling devices that consume power to maintaintemperature of the laser transceiver node 120 at a single temperature,the laser transceiver node 120 can comprise one or more passivetemperature controlling devices 450 that do not consume power. Thepassive temperature controlling devices 450 can comprise one or moreheat sinks or heat pipes that remove heat from the laser transceivernode 120. Those skilled in the art will appreciate that the presentinvention is not limited to these exemplary passive temperaturecontrolling devices. Further, those skilled in the art will alsoappreciate the present invention is not limited to the exemplaryoperating temperature range disclosed. With appropriate passivetemperature controlling devices 450, the operating temperature range ofthe laser transceiver node 120 can be reduced or expanded.

In addition to the laser transceiver node's 120 ability to withstandharsh outdoor environmental conditions, the laser transceiver node 120can also provide high speed symmetrical data transmissions. In otherwords, the laser transceiver node 120 can propagate the same bit ratesdownstream and upstream to and from a network subscriber. This is yetanother advantage over conventional networks, which typically cannotsupport symmetrical data transmissions as discussed in the backgroundsection above. Further, the laser transceiver node 120 can also serve alarge number of subscribers while reducing the number of connections atboth the data service hub 110 and the laser transceiver node 120 itself.

The laser transceiver node 120 also lends itself to efficient upgradingthat can be performed entirely on the network side or data service hub110 side. That is, upgrades to the hardware forming the lasertransceiver node 120 can take place in locations between and within thedata service hub 110 and the laser transceiver node 120. This means thatthe subscriber side of the network (from distribution optical waveguides150 to the subscriber optical interfaces 140) can be left entirelyin-tact during an upgrade to the laser transceiver node 120 or dataservice hub 110 or both.

The following is provided as an example of an upgrade that can beemployed utilizing the principles of the present invention. In oneexemplary embodiment of the invention, the subscriber side of the lasertransceiver node 120 can service six groups of 16 subscribers each for atotal of up to 96 subscribers. Each group of 16 subscribers can share adata path of about 450 Mb/s speed. Six of these paths represents a totalspeed of 6×450=2.7 Gb/s. In the most basic form, the data communicationspath between the laser transceiver node 120 and the data service hub 110can operate at 1 Gb/s. Thus, while the data path to subscribers cansupport up to 2.7 Gb/s, the data path to the network can only support 1Gb/s. This means that not all of the subscriber bandwidth is useable.This is not normally a problem due to the statistical nature ofbandwidth usage.

An upgrade could be to increase the 1 Gb/s data path speed between thelaser transceiver node 120 and the data service hub 110. This may bedone by adding more 1 Gb/s data paths. Adding one more path wouldincrease the data rate to 2 Gb/s, approaching the total subscriber-sidedata rate. A third data path would allow the network-side data rate toexceed the subscriber-side data rate. In other exemplary embodiments,the data rate on one link could rise from 1 Gb/s to 2 Gb/s then to 10Gb/s, so when this happens, a link can be upgraded without adding moreoptical links.

The additional data paths (bandwidth) may be achieved by any of themethods known to those skilled in the art. It may be accomplished byusing a plurality of optical waveguide transceivers 430 operating over aplurality of optical waveguides, or they can operate over one opticalwaveguide at a plurality of wavelengths, or it may be that higher speedoptical waveguide transceivers 430 could be used as shown above. Thus,by upgrading the laser transceiver node 120 and the data service hub 110to operate with more than a single 1 Gb/s link, a system upgrade iseffected without having to make changes at the subscribers' premises.

FIG. 6 is a functional block diagram illustrating another exemplaryoutdoor laser transceiver node 120B that employs dual transceiversbetween tap multiplexers 440 and respective groups of subscribers. Inthis embodiment the downstream optical signals originating from eachrespective tap multiplexer 440 are split immediately after the tapmultiplexer 440. In this exemplary embodiment, each optical transmitter325 is designed to service only eight subscribers as opposed to sixteensubscribers of other embodiments. But each tap multiplexer 440 typicallyservices sixteen or fewer subscribers.

In this way, the splitting loss attributed to the optical taps 130placed further downstream relative to the tap multiplexers 440 can besubstantially reduced. For example, in other exemplary embodiments thatdo not split the downstream optical signals immediately after the tapmultiplexer 440, such embodiments are designed to service sixteen orfewer subscribers with a corresponding theoretical splitting loss ofapproximately 14 dB (including an allowance for losses). With thecurrent exemplary embodiment that services eight or fewer subscribers,the theoretical splitting loss is reduced to approximately 10.5 dB.

In laser transceiver node 120B, the outputs of two optical receivers 370cannot be paralleled because at all times one receiver 370 or the otheris receiving signals from respective subscribers, while the otherreceiver 370 is not receiving signals. The receiver 370 not receivingany upstream optical signals could output noise which would interferewith reception from the receiver 370 receiving upstream optical signals.Therefore, a switch 1105 can be employed to select the optical receiver370 that is currently receiving an upstream optical signal. The tapmultiplexer 440 can control the switch 1105 since it knows which opticalreceiver 370 should be receiving upstream optical signals at any givenmoment of time.

However, since the RF return system of the present invention preservesthe data collision detection scheme of the legacy video servicescontroller 115, there may be instances when the tap multiplexer 440 isnot aware of upstream RF packets. In other words, since the tapmultiplexer 440 operates independently of the video services controller115, it does not have any information about the sequence in which videoservice terminals 117 are transmitting upstream RF information. Also,the tap multiplexer 440 may not be aware of new subscriber opticalinterfaces 140 that are added to the system and who are not registeredwith the tap multiplexer 440. In these scenarios, the tap multiplexer440 may not know in which position to place switch 1105. Aserializer/deserializer circuit (SERDES—not shown but known to thoseskilled in the art) that typically follows the switch 1105 and is partof tap multiplexer 440, may loose synchronization if it doesn't receivea signal for some short length of time.

Therefore, each optical receiver 370 may comprise a signal detector line372 that is coupled to a driver 374. The driver 374 is connected to theswitch 1105. The signal detector line 372 may comprise hardware builtinto a respective optical receiver that is designed to detect a presenceof an optical signal as it enters a respective optical receiver 370. Thesignal detector line 372 is typically designed to check for the presenceof an optical signal during very short intervals that are usuallysmaller than the interstitial intervals (the time between transmissionsof multiple RF packets from different subscriber optical interfaces140).

Referring now to FIG. 7, this Figure illustrates a functional blockdiagram of an exemplary laser transceiver node 120C that providesadditional detail of hardware that supports multiple RF packetsoriginating from multiple video service terminals 117. Only thedifferences between FIG. 6 and FIG. 7 will be discussed below.

RF packets from the subscriber optical interfaces 140 typically enterthe laser transceiver node 120 as a burst, located in time between othertypes of regular upstream packet data. The RF packets are separated fromthe other upstream packet data in the optical tap routing device 435.The RF packets are slowed down by a respective data conditioner 407, andthen are applied to an adder 313, which combines all data burstsregardless of which optical tap routing device 435 forwarded the RFpackets. Since only one return path is active at a time, by virtue ofthe management of time slots by the video services controller 115, thenall inputs to the adder 313 are zero except the active input.

It is noted that the conversion from digital RF packets to analog RFsignals will not take place until the RF packets are received at thedata service hub 110. As noted above, the RF packets are slowed down atthe laser transceiver node 120 to reduce the demands on the transmissionpath back to the data service hub 110.

Referring now to FIG. 8, this Figure is a functional block diagramillustrating an optical tap 130 connected to a subscriber opticalinterface 140 by a single optical waveguide 150 according to oneexemplary embodiment of the present invention. The optical tap 130 cancomprise a combined signal input/output port that is connected toanother distribution optical waveguide that is connected to a lasertransceiver node 120. As noted above, the optical tap 130 can comprisean optical splitter 510 that can be a 4-way or 8-way optical splitter.Other optical taps having fewer or more than 4-way or 8-way splits arenot beyond the scope of the present invention.

The optical tap 130 can divide downstream optical signals to serverespective subscriber optical interfaces 140. In the exemplaryembodiment in which the optical tap 130 comprises a 4-way optical tap,such an optical tap can be of the pass-through type, meaning that aportion of the downstream optical signals is extracted or divided toserve a 4-way splitter contained therein, while the rest of the opticalenergy is passed further downstream to other distribution opticalwaveguides 150.

The optical tap 130 is an efficient coupler that can communicate opticalsignals between the laser transceiver node 120 and a respectivesubscriber optical interface 140. Optical taps 130 can be cascaded, orthey can be connected in a star architecture from the laser transceivernode 120. As discussed above, the optical tap 130 can also route signalsto other optical taps that are downstream relative to a respectiveoptical tap 130.

The optical tap 130 can also connect to a limited or small number ofoptical waveguides so that high concentrations of optical waveguides arenot present at any particular laser transceiver node 120. In otherwords, in one exemplary embodiment, the optical tap can connect to alimited number of optical waveguides 150 at a point remote from thelaser transceiver node 120 so that high concentrations of opticalwaveguides 150 at a laser transceiver node can be avoided. However,those skilled in the art will appreciate that the optical tap 130 can beincorporated within the laser transceiver node 120 with respect toanother exemplary embodiment (not shown).

The subscriber optical interface 140 functions to convert downstreamoptical signals received from the optical tap 130 into the electricaldomain that can be processed with appropriate communication devices. Thesubscriber optical interface 140 further functions to convert upstreamdata and RF packet electrical signals into upstream optical signals thatcan be propagated along a distribution optical waveguide 150 to theoptical tap 130.

The subscriber optical interface 140 can comprise an optical diplexer515 that divides the downstream optical signals received from thedistribution optical waveguide 150 between a bi-directional opticalsignal splitter 520 and an analog optical receiver 525. The opticaldiplexer 515 can receive upstream optical signals generated by a digitaloptical transmitter 530. The digital optical transmitter 530 convertselectrical binary/digital signals such as upstream data packets and RFpackets to optical form so that the optical signals can be transmittedback to the data service hub 110. Conversely, the digital opticalreceiver 540 converts optical signals into electrical binary/digitalsignals so that the electrical data signals can be handled by processor550. Processor 550 can comprise an application specific integratedcircuit (ASIC) in combination with a central processing unit (CPU).However, other hardware implementations are not beyond the scope andspirit of the present invention.

The RF return system of the present invention can propagate the opticalsignals at various wavelengths. However, the wavelength regionsdiscussed are practical and are only illustrative of exemplaryembodiments. Those skilled in the art will appreciate that otherwavelengths that are either higher or lower than or between the 1310 and1550 nm wavelength regions are not beyond the scope of the presentinvention.

The analog optical receiver 525 can convert the downstream broadcastoptical video signals into modulated RF television signals anddownstream video service control signals into analog RF signals that arepropagated through an RF diplexer 507 and out of the modulated RF signalinput/output 535. The modulated RF bidirectional signal input/output 535can feed into the video services terminal 117. The video servicesterminal 117 can be coupled to a tuner 503 that comprises a televisionset or radio. The analog optical receiver 525 can process analogmodulated RF transmission as well as digitally modulated RFtransmissions for digital TV applications.

The bi-directional optical signal splitter 520 can propagate combinedoptical signals in their respective directions. That is, downstreamoptical signals entering the bi-directional optical splitter 520 fromthe optical the optical diplexer 515, are propagated to the digitaloptical receiver 540. Upstream optical signals entering it from thedigital optical transmitter 530 are sent to optical diplexer 515 andthen to optical tap 130. The bi-directional optical signal splitter 520is connected to a digital optical receiver 540 that converts downstreamdata optical signals into the electrical domain. Meanwhile thebi-directional optical signal splitter 520 is also connected to adigital optical transmitter 530 that converts upstream data packet andRF packet electrical signals into the optical domain.

The digital optical receiver 540 can comprise one or more photoreceptorsor photodiodes that convert optical signals into the electrical domain.The digital optical transmitter 530 can comprise one or more lasers suchas the Fabry-Perot (F-P) Lasers, distributed feedback lasers, andVertical Cavity Surface Emitting Lasers (VCSELs). Other types of lasersare within the scope and spirit of the invention.

The digital optical receiver 540 and digital optical transmitter 530 areconnected to a processor 550 that selects data intended for the instantsubscriber optical interface 140 based upon an embedded address. Thedata handled by the processor 550 can comprise one or more of telephonyand data services such as an Internet service. The processor 550 isconnected to a telephone input/output 560 that can comprise an analoginterface. The processor 550 is also connected to a data interface 555that can provide a link to computer devices, ISDN phones, and other likedevices. Alternatively, the data interface 555 can comprise an interfaceto a Voice over Internet Protocol (VoIP) telephone or Ethernettelephone. The data interface 555 can comprise one of Ethernet (10BaseT,100BaseT, Gigabit) interface, HPNA interface, a universal serial bus(USB) an IEEE1394 interface, an ADSL interface, and other likeinterfaces.

When the video services terminal 117 generates RF signals, these RFsignals are propagated through the modulated RF signal input/output 535to the diplexer 507. The diplexer 507 passes the upstream analog RFsignals to an analog-to-digital (A/D) converter 509. From the A/Dconverter 509, the digital RF signals are passed to a data reducer 511.Further details of the data reducer 511 will be discussed below withrespect to FIG. 10 a. The reduced RF signals are then propagated to adata conditioner 407. The data conditioner 407 at this stage can speedup data transmission of the RF signals. The data conditioner 407 cancomprise a buffer such as a FIFO that also inputs a time stamp andidentification information with the digitized RF signals to form RFpackets. That is, an RF packet can comprise digitized and reduced RFsignals that are coupled with identification and timing information.Reduced RF signals may enter the data conditioner 407 at an exemplarytransmission speed of 40 Megabits per second (Mps) while the newlyformed RF packets exit the data conditioner 407 at an exemplarytransmission speed of 500 Megabits per second (Mps). However, othertransmission speeds are not beyond the scope of the present invention.

RF packets are transferred upstream from the data conditioner 407 when aswitch 513 connects the data conditioner 407 to the digital opticaltransmitter 530. The switch 513 is controlled by processor 550. Whenswitch 513 is not connected to the data conditioner 407, it can connectthe output of the processor 550 to the digital optical transmitter 530.In other words, the switch 513 may be activated at appropriate times tocombine the upstream RF packets from the data conditioner 407 withupstream data packets from the processor 550 destined for the dataservice hub 110. More specifically, the RF packets may be insertedbetween upstream packets comprising data generated by a subscriber witha communication device such as a computer or telephone. The insertionsbetween regular upstream data packets are referred to as “intersititals”as will be discussed in further detail below with respect to FIGS. 13and 14.

In one exemplary embodiment, the regular upstream data packets are keptin tact meaning that the processor 550 determines what upstream datapackets can fit between the interstitials. In other words, in oneexemplary embodiment, the processor 550 does not break any upstream datapackets. However, in another exemplary embodiment (not shown), it ispossible for processor 550 to break or separate upstream packets intosmaller packets so that they will fit between the interstitials. Sincethe breaking and reforming of packets is known to those skilled in theart, a detailed discussion of packet breaking and reforming methods willnot be discussed herein.

The insertion of RF packets between regular data packets for upstreamtransmission is yet one important feature of the invention. In otherwords, the timing at which the RF packets are inserted between upstreamdata packets for upstream transmission is one inventive aspect of thepresent invention. The amount of time between RF packet transmissions istypically smaller than the amount of time allotted for the production ofthe analog RF signal produced by the video service terminal 117.

Stated differently, the size of the RF signal produced by the videoservice terminal 117 as measured in time is usually greater than theamount of time between upstream transmissions of a pair of RF packets.While the upstream transmission of data packets is interrupted atintervals with upstream RF packet transmission, it is noted that theintervals of interruption do not need to be regularly spaced from oneanother in time. However, in one exemplary embodiment, the interruptionsare designed to be spaced at regular, uniform intervals from oneanother. With the present invention, the upstream transmission of RFpackets can occur with very low latency and jitter.

It is noted that the switch 513 of each subscriber optical interface 140is activated at the same time. In other words, each switch 513 of eachsubscriber optical interface 140 checks for RF packets from a respectivedata conditioner 407 at the same time. While such functionality mayappear to contribute to possible data collisions between respectivevideo service terminals 117, the video service controller 115 actuallyprevents any data collisions between respective RF packets of differentsubscriber optical interfaces 140. That is, another unique feature ofthe RF return system of the present invention is that the timing betweenlegacy video service terminal transmissions is typically not controlledby the present invention.

The RF return system of the present invention actually preserves theupstream transmission timing scheme that is controlled by the legacyvideo service controller 115 that is housed within the data service hub110. The upstream transmission timing scheme generated by the legacyvideo service controller 115 is designed to eliminate any collisionsbetween RF signals produced by different video service terminals 117.The present invention operates independently of this legacy upstreamtransmission timing scheme so that the legacy upstream transmissiontiming scheme can remain effective.

Referring now to FIG. 9, this Figure illustrates a functional blockdiagram of an overview of the aforementioned architecture that forms theRF return path for RF signals originating from a video service terminal117. The RF signals to be returned from the video service terminal 117in a subscriber's home is propagated towards the modulated RFinput/output signal interface 535 near the lower right corner of thesubscriber optical interface 140. Each RF return signal can comprise afrequency that exists between an exemplary range of 5 and 42 MHz inNorth America. The RF signal can comprise an occasional burst of RFmodulated data, which must be transported back to the headend. Becauseof certain design parameters of legacy video service systems that workaccording DVS 167 and DVS 178 standards, it is recommended that themodulated RF signal be delivered back to the data service hub 110 in atime frame comprising approximately one millisecond. However, other timeframes of different magnitudes are not beyond the scope of the presentinvention.

The modulated RF signal between 5 and 42 MHz generated by the videoservice terminal 117 is routed to the low frequency port of an RFdiplexer 507. This signal is digitized in A/D converter 509, processedin the data reducer 511 and data conditioner 407. While in the datareducer 511, certain algorithms are applied to reduce the amount of datatransmitted. A number of algorithms related to subsampling and othertechniques are known to those skilled in the art. Further details of thedata reducer 511 will be discussed below with respect to FIG. 10 a.

Then during an interstitial time period, a switch 513 connects the dataconditioner 407 to the digital optical transmitter 530. During thisconnection, the RF packets are transmitted upstream with the digitaloptical transmitter 530. The present invention is not limited to adiscrete switch 513 as described above. The switch functionality may beincorporated into the processor 550 or other appropriate hardware devicein the subscriber optical interface 140.

At the laser transceiver node 120, both upstream data packets and RFpackets are received in laser optical receiver 370, which receives datafrom a number of different subscriber optical interfaces 140. In thedata conditioner 407 of the laser transceiver node 120, the RF packetsare slowed to the speed at which they will ultimately be converted backto analog RF signals. The RF packets are supplied to a low speed datatransmitter 325, which transmits the digital RF packets from all videoservice terminals 117 back to the data service hub 110, via an opticaldiplexer 420.

At the data service hub 110, the RF optical packets are received andconverted into the electrical domain by a low speed data receiver 370,and then are converted to analog RF signals in the data-to-RF converter307, and supplied to the video services control receiver 309. The videoservice control receiver 309 demodulates the analog RF signals andpasses them to the video service controller 115. One key feature of theinvention is the recognition that the video service controller 115itself will manage time slots for video service terminal 117, ensuringthat no two RF data packets using the same video service controlreceiver 309, will transmit at the same time. Because of thischaracteristic, it is not necessary for the system of the presentinvention to manage time slots for the video service terminals 117.

An alternative exemplary embodiment (not shown) that is useful incertain situations, is to use a separate fiber for upstreamtransmission, allowing the elimination of diplexers 420 in both thelaser transceiver node 120 and data service hub 110, and reducing thelosses of the downstream signals on fiber 160.

Referring now to FIG. 10 a, this figure illustrates a functional blockdiagram that describes further details of a data reducer 511. The RFsignals produced by each video service terminal may comprise signalsthat bear digital modulation usually but not necessarily QPSKmodulation. These RF signals are supplied from the video serviceterminal 117 to RF diplexer 507, which separates the higher-frequencydownstream RF signals from the lower-frequency upstream signals. Thelower frequency upstream signal typically comprises a singlelimited-bandwidth RF signal. It is one object of the present discussionto capture this analog RF signal, convert it to digital form and relayit back to the headend, where it is converted back to an analog RFsignal that can be received by a video service control receiver 309.

Data from the low port of RF diplexer 507 is supplied to an RF signaldetector 517, which determines when an analog RF signal is present. Whena signal appears, RF signal detector 517 notifies a controller 519 ofthe presence of the signal, and controller 519 initiates a series ofsteps. Controller 519 receives time stamps from laser transceiver node120. The time stamp can comprise a sequential word that is transmittedfrom laser transceiver node 120, related to a time-keeping functionperformed in laser transceiver node 120. Normally, the controller 519discards a time stamp as soon as the next one is received. However, ifRF signal detector 517 detects an RF signal coming from the videoservice terminal 117, then the time stamp that applies at that instantis passed on to data conditioner 407, for incorporation in the RF packetdata output. This function will be described below.

When an RF signal is received and detected by RF signal detector 517,then it is converted to digital form in A/D converter 509. Prior tobeing converted to digital form, it is sampled in the sample-and-holdfunction, switch 521 and hold capacitor 523. This sample and holdfunction is well-known to those skilled in the art. Switch 521 is closedperiodically, resulting in the voltage on the low port of diplexer 507being transferred to capacitor 523. Then switch 521 is opened, and thevoltage remains on capacitor 523 while A/D converter 509 converts thevoltage to a digital word. The digital word typically must comprise aminimum number of bits in order to provide an adequate signal-to-noiseratio (S/N) for recovering the data, as is understood by those skilledin the art.

For recovery of QAM, it is estimated that four bits will yield anadequate S/N. However, this assumes that the signal occupies the entirefour bit range. If the signal is too low in amplitude it will not betransmitted at reasonable S/N, and if the signal is of too great anamplitude, it will clip the A/D converter 509 and will fail to supply auseable signal to RF video service control receiver 309. The videoservice terminal control system described in DVS 167 and DVS 178includes the ability to smooth the video service terminal output to therequired level or amplitude, but when a video service terminal 117 isfirst added to the system, its level is not correct. Thus, the A/D musthave adequate range to digitize the signal even if it is at theincorrect amplitude.

Those skilled in the art know that the minimum rate at which the signalcan be sampled is twice the highest frequency of the signal beingsampled. This limitation is known as the Nyquist sampling theorem. Thisis illustrated in FIG. 10 b that depicts a graph 526. The samplingfrequency, f_(S), at which switch 521 is cycled, usually must be morethan twice the highest frequency in the RF return signal. This highestfrequency is represented by f_(H). Thus, the sampling frequency f_(S)must be equal to or greater than 2 times f_(H).

The data rate needed to support data transmission is given by theproduct of the sampling frequency f_(S) and the number of bitstransmitted, n. Thus, if 8 bits are needed to transmit an adequate S/N(allowing for errors in signal level), and f=15 MHz, the minimum datarate is 2×15×8, or 240 Mb/s. In practice, a higher data rate must beused, to compensate for limitations of real filters. Two methods areused to reduce the data rate that must be transmitted. First, thefrequency of the signal is reduced, then the number of bits of data isreduced by scaling the amplitude of the digitized signal (data scaling).These methods will be explained below.

After A/D converter 509, the digital signal is propagated to the dataconditioner 511. The data conditioner 511 can comprise a down conversionprocessing unit 527 and a low pass filter 529. Down conversionprocessing unit 527 comprises a mixing (multiplication) process thattakes place in the digital domain. This function may also be implementedin the RF domain before switch 521, as is understood by those skilled inthe art. In the down conversion unit 527, each sample of the digitizedsignal is multiplied by a number representing a sinusoidal waveform. Thenumber representing a sinusoidal waveform is generated in the digitaldomain, f_(LO) 531, as illustrated in FIG. 10 c, and is the localoscillator signal shown in the small spectrum diagram near the bottom ofFIG. 10 c.

As is understood by those skilled in the art, when the RF return signalis mixed with f_(LO) 531, either in the digital domain shown or in theRF domain, several components are generated. These include thedifference signal 533, the sum signal 534, and a number of harmonics536. All of these components with the exception of the difference 533,are removed by low pass filter 529, whose shape is shown by the dashedline 537. As is understood by those skilled in the art, it is sometimespossible to set f_(LO) equal to the carrier frequency of the incomingsignal (usually equal to (f_(H)-f_(L))/2). This can result in the lowestpossible data rate.

Since the frequency of the sampled signal is now lower, being thedifference frequency 533, the number of times the signal is sampled maybe reduced without violating the Nyquist sampling theorem. Thisoperation is performed in sample elimination unit 538, which removesunnecessary samples. In a simple case, this function may be performed bysimply dropping every other sample point, or by dropping two of threesampling points, etc. In a more sophisticated sample reductionalgorithm, the sampling rate may be reduced by choosing sampling timesand interpolating between samples of the incoming signal. This techniqueis understood by those skilled in the art.

The data scaling unit 539 removes unnecessary numbers of bits from eachsample, while maintaining the maximum scaling of the data. The techniqueis familiar to those skilled in the art, and for example has been usedin the British NICAM (Near Instantaneous Compression and Modulation)method of transmitting digital audio information on an analog channel.

FIG. 10 d illustrates one exemplary data scaling algorithm 1000 that canbe performed by data scaling unit 539. The description of the flowcharts in the this detailed description are represented largely in termsof processes and symbolic representations of operations by conventionalcomputer components, including a processing unit (a processor), memorystorage devices, connected display devices, and input devices.Furthermore, these processes and operations may utilize conventionaldiscrete hardware components or other computer components in aheterogeneous distributed computing environment, including remote fileservers, computer servers, and memory storage devices. Each of theseconventional distributed computing components can be accessible by theprocessor via a communication network.

The processes and operations performed below may include themanipulation of signals by a processor and the maintenance of thesesignals within data structures resident in one or more memory storagedevices. For the purposes of this discussion, a process is generallyconceived to be a sequence of computer-executed steps leading to adesired result. These steps usually require physical manipulations ofphysical quantities. Usually, though not necessarily, these quantitiestake the form of electrical, magnetic, or optical signals capable ofbeing stored, transferred, combined, compared, or otherwise manipulated.It is convention for those skilled in the art to refer torepresentations of these signals as bits, bytes, words, information,elements, symbols, characters, numbers, points, data, entries, objects,images, files, or the like. It should be kept in mind, however, thatthese and similar terms are associated with appropriate physicalquantities for computer operations, and that these terms are merelyconventional labels applied to physical quantities that exist within andduring operation of the computer.

It should also be understood that manipulations within the computer areoften referred to in terms such as creating, adding, calculating,comparing, moving, receiving, determining, identifying, populating,loading, executing, etc. that are often associated with manualoperations performed by a human operator. The operations describedherein can be machine operations performed in conjunction with variousinput provided by a human operator or user that interacts with thecomputer.

In addition, it should be understood that the programs, processes,methods, etc. described herein are not related or limited to anyparticular computer or apparatus. Rather, various types of generalpurpose machines may be used with the following process in accordancewith the teachings described herein.

The present invention may comprise a computer program or hardware or acombination thereof which embodies the functions described herein andillustrated in the appended flow charts. However, it should be apparentthat there could be many different ways of implementing the invention incomputer programming or hardware design, and the invention should not beconstrued as limited to any one set of computer program instructions.Further, a skilled programmer would be able to write such a computerprogram or identify the appropriate hardware circuits to implement thedisclosed invention without difficulty based on the flow charts andassociated description in the application text, for example. Therefore,disclosure of a particular set of program code instructions or detailedhardware devices is not considered necessary for an adequateunderstanding of how to make and use the invention. The inventivefunctionality of the claimed computer implemented processes will beexplained in more detail in the following description in conjunctionwith the remaining Figures illustrating other process flows.

Certain steps in the processes or process flow described below mustnaturally precede others for the present invention to function asdescribed. However, the present invention is not limited to the order ofthe steps described if such order or sequence does not alter thefunctionality of the present invention. That is, it is recognized thatsome steps may be performed before or after other steps withoutdeparting from the scope and spirit of the present invention.

FIG. 10 d uses an example of reducing an 8 bit sample down to 4 bits,though other reductions can be used and are not beyond the scope of thepresent invention. The algorithm starts at step 1005. A counter, calledan MSB (most significant bit) counter is used in the routine to keeptrack of the number of places on the left of a data word have beeneliminated, as will be evident from the description below. The MSBcounter is initially set to a count of 0 in step 1010.

In step 1015, a block of data, such as, but not limited to, thirty-two8-bit bytes, are read and processed. Within that block of data, eachsample is examined in step 1020 to determine if the MSB is a 1 or a 0.If all samples in the block have a 0 in the MSB position, then theinquiry to decision step 1020 is answered “No”, meaning that the MSB isnot used in any data in that set of bytes. If the inquiry to decisionstep 1020 is negative, then the “No” branch is followed to step 1025 inwhich the data may be shifted left. At the same time, the MSB counterreferred to above is incremented by 1, to keep track of how many timesthe block has been shifted. Operation then returns to decision step1020, which again decides whether the MSB is used. If not, then theprocess repeats through step 1020, until the MSB is used. Note that thisprocess applies to all the data words in the block of data beingprocessed.

When the MSB is used, then the inquiry to decision step 1020 is positiveand the “Yes” branch is followed to step 1030 in which the leastsignificant four bits of the word are dropped. Thus, the routine 1000has caused the retention of the four most significant bits that havedata, in the block of data. These bits are transmitted in step 1035along with the state of the MSB counter, which is used to reconstructthe waveform at the data service hub 110.

Referring now to FIG. 11 a, this figure illustrates a functional blockdiagram that describes further details of a data-to-RF converter 307.The time stamp that is added by the data conditioner 407 in thesubscriber optical interface 140 controls initiation of the analog RFsignal recovery process discussed below. That time stamp is eitheroperative in the data-to-RF converter 307 of the data service hub 110,or in the data conditioner 407 of the laser transceiver node 120. Eitherplace is satisfactory.

When the RF packets are returned to the data-to-RF converter 307 at thedata service hub 110, they usually must be restored to their originalform. In the scaling restoration unit 317, the data scaling of the RFanalog signals represented in the RF packet is restored, reversing theactions performed by the data scaling unit 539 of the data reducer 511.

FIG. 11 b illustrates the scaling restoration process. Certain steps inthe process described below must naturally precede others for thepresent invention to function as described. However, the presentinvention is not limited to the order of the steps described if suchorder or sequence does not alter the functionality of the presentinvention. That is, it is recognized that some steps may be performedbefore or after other steps without departing from the scope, and spiritof the present invention.

The restoration process starts at step 1105. The value of the MSBcounter is read in step 1110, then data is read in 1115. For each dataword, the data is shifted right by the MSB counter value in step 1120,with leading zeros being added to the left of the transmitted bits.Thus, the value that was originally developed in the sample eliminationunit 538, is restored. Of course, if fewer than the four mostsignificant bits in the original word have been dropped, then some leastsignificant bits are converted to zero by the process, but theyrepresent only small errors in the recovered signal, and are tolerable.

In decision step 1125, it is determined whether all of the data thecurrent transmission or block has been read. If the inquiry to decisionstep 1125 is negative, then the “No” branch is followed back to step1115. If the inquiry to decision step 1125 is positive, then the “Yes”branch is followed to step 1130 where the data scaling restorationprocess ends.

Referring back to FIG. 11 a, in the sampling restoration unit 319, thesampling is restored to the original sampling rate by adding samplesbetween the transmitted samples. Interpolating between transmittedsamples is understood by those skilled in the art. The frequency of thesignal is up-converted to the original frequency in the frequency upconverter 321, by mixing it with a local oscillator signal as shownabove. Next the signal is filtered by bandpass filter 323. The signal isthen converted to analog form in D/A converter 324. Thus, at the outputof D/A converter 324 is the data from the Low port of the RF diplexer507 of the subscriber optical interface 140, which was supplied to theinput of the sample and hold circuit 521 and 523 of FIG. 10 a.

Referring now to FIGS. 12 and 13, these figures illustrate thecomputation of the burst process for upstream RF packets of an exemplaryembodiment. In this exemplary embodiment, each video service terminal117 is bursting data in packets that are 333 microseconds long. Theoccupied bandwidth is an exemplary 3.2 MHz, based on the worst-caseDOCSIS return bandwidth. However, other bandwidths may be used in thecalculation without departing from the spirit and scope of the presentinvention.

It is recommend that sampling occurs at twice this rate, or 6.4 Ms/s(mega, or million, samples per second). Sampling at a greater amount,such as at 8 Ms/s, may provide some safety margin and to make frequencyselection somewhat easier. If sampling occurs at four bits per sample(16 levels—adequate for QPSK and possibly for 16 QAM modulation withcareful level control), this yields a data rate of 32 Mb/s as shown.Some overhead may be needed, so the data rate can be rounded up to 40Mb/s as the required data rate.

A typical burst length is 333 microseconds from the DVS 167specification referenced above. In an exemplary embodiment, the datatransmission on an optical waveguide is 500 Mb/s, so if a 40 Mb/s signaltransmission speed is increased to a transmission speed of 500 Mb/s, itwill require

$\frac{40}{500} = {8\%}$of the available bandwidth. Therefore, a 333 microseconds burst willrequire a transmission time of

${333\frac{40}{500}} = {26.64\mspace{20mu}\mu\;{s.}}$

Because of the detailed requirements of the data transmission methodused, this RF packet usually must be returned to the data service hub110 and converted back to analog RF with a delay not to exceed just over2 milliseconds (ms), and with very low jitter. However, other magnitudesof delay, smaller or larger, are not beyond the scope of the presentinvention.

If the bursts were simply packetized and sent back to the data servicehub 110, there would be many milliseconds of jitter introduced by thepacketized Ethernet transmission system. Thus, the invention teaches amethod of getting the bursts of data back to the data service hub 110outside of the normal method of handling packets, but without undulyburdening the cost of the equipment. The shaded box 1300 in FIG. 13represents an interstitial burst comprising the RF packet data.

Referring now to FIG. 14, this figure is a diagram that illustrates atiming scheme 1400 of the return RF analog signals and the rules forhandling the RF packets produced from the RF analog signals. Row 1 ofFIG. 14 illustrates the video service controller system time marks 1405generated by the video services controller 115. These marks 1405 arespaced by the width 1410 of a video service terminal time slot, t_(VST).The time marks 1405 indicate time as perceived at the data service hub110. Time may be perceived as occurring later at all subscriber opticalinterfaces 140, due to propagation delay. The video services controller115 will cause the transmission time of each video service terminal 117,located at each subscriber optical interface 140, to be advanced as muchas is necessary to make the response arrive at the video servicecontroller 115 at the correct time. The time marks 1405 of row 1indicate the boundaries at which the video service terminal upstreamtransmissions are expected to be received by the video servicecontroller 115.

In one exemplary embodiment, the time scale is such that there are sevenunits of time in a width of t_(VST) 1410. Thus, a time offset of oneunit will cause the packet time to be displaced by one-seventh of thedistance between two time marks in row 1 or

$\frac{333}{7} = {47.57\mspace{20mu}\mu\;{s.}}$

Row 2 of FIG. 14 illustrates the transmission of RF packets at thesubscriber optical interface 140. The data reducer 511 applies a datacompression technique to the digitized RF packets in order to conservereturn bandwidth. These RF packets are digitized by the A/D converter509 of FIG. 8. The larger rectangles 1415 represent the time availablefor a video service terminal 117 to transmit. The smaller, clear,rectangles 1420 within the larger rectangles represent the time thevideo service terminal 117 actually transmits the RF packets. Thetransmission time may be shorter or longer than a video service terminaltime slot width or t_(VST) 1410. The letters above row 2 refer to theeach of a plurality of subscriber optical interfaces 140 which can betreated as a group by the video service controller 115. These letterswill be used in an example below.

Examining row 2 of FIG. 14, one recognizes that a video service terminal117 associated with subscriber optical interface F does not transmit anyRF packets. This is the rule rather than the exception: most of thetime, it is assumed that each video service terminal 117 will not senddata in a particular time slot. The problem with this rule is that theRF return system of the present invention does not know when a videoservice terminal 117 will want a particular time slot to transmit its RFpackets. As noted above, the RF return system of the present inventionand the legacy video services system operate independently of eachother. That is, each terminal time slot or t_(VST) 1410 is assigned andmanaged by the video service system controller 115 independently of theRF return system of the present invention which is responsible forcarrying the return RF packets back to the data service hub 110.

The video service controller 115 does not permanently assign any timeslot 1410. Each time a video service terminal 117 needs to transmit RFpackets, it must compete for a time slot 1410, and when it is assignedone, it transmits its RF packets and then releases the time slot 1410.Thus, the example illustrated in FIG. 14 applies only to one instance oftime. In another instances, other video service terminals 117 will betransmitting in the time slots shown.

Row 3 of FIG. 14 illustrates the interstitials 1300 that comprise the RFpackets as they are transmitted out in interstitial bursts betweennon-video service terminal or regular data packets 1425. Row 3 iscombined data as perceived by the optical tap routing device 435 or anadder 313 of an optical tap routing device 120. The non-video serviceterminal or regular data packets 1425 are generated by processor 550, inresponse to equipment serviced by the processor 550 such as computers,telephones, and other like data producing equipment as illustrated inFIG. 8. Regular data packets 1425 other than video service terminal data(“non-video service terminal data”) is transmitted during most of thetime, indicated by the hatched area in row 3.

RF packets within the interstitials 1300 are transmitted duringinterstitial times between the other data packets 1425. The timing oftransmission for the interstitials 1300 is determined by the presentinvention rather than by the legacy video service controller 115. Theinterstitials 1300 of Row 3 also represent the instance of time eachswitch 513 of respective subscriber optical interfaces 140 asillustrated in FIG. 8 is connecting a respective data conditioner 407 torespective digital optical transmitter 530. The length of time betweentransmission of interstitials 1300 is referred to as an interstitialinterval or t_(INSTL) 1430. In order to correctly transmit RF packets tothe video service controller 115, it is necessary for each interstitialinterval, t_(INSTL) 1430 to be less than a terminal time slot, t_(VST)1410. If an interstitial interval, t_(INSTL) 1430 is substantially equalto or greater than a terminal time slot, t_(VST) 1410, then it ispossible that there will be two different video service terminals 117trying to transmit during adjacent terminal time slots or t_(VST) 1410and in the process of relaying the RF packets back to the video servicecontroller 115, there can be a data collision.

A rule that can be applied at the subscriber optical interface 140 isthat the interstitials 1300 are burst or transmitted at regularintervals having a magnitude of t_(INSTL) 1430. This means that allsubscriber optical interfaces 140 that are normally timed together by acommon port on the laser transceiver node 120 have the same interstitialburst time. This means, as mentioned above, that each switch 513 of agroup of respective subscriber optical interfaces 140 connects arespective data conditioner 407 to a respective digital opticaltransmitter 530 at the same time. Though usually, it is assumed thatnothing will be transmitted from any one subscriber optical interface140 when the switches 513 connect to each data conditioner 407. In otherwords, most of the time, video service terminals 117 do not transmit anydata.

When a video service terminal 117 does have something to transmit, itwill send the analog RF signal to the subscriber optical interface,where the analog RF signal is digitized in A/D converter 509. Thedigitized RF packet may last up to the maximum time interval t_(VST)1410, but may last a shorter time if less information is to betransmitted. The actual time the packet lasts is the “actual time used”1420 as illustrated in row 2 of FIG. 14. A video service terminal 117may transmit for longer than t_(VST) 1410, in which case two or moreadjacent time terminal slots 1410 are used by the same video serviceterminal 117. In order for a video service terminal 117 to transmitduring two consecutive video service terminal time slots 1410, it mustrequest permission from the video service controller 115.

When the A/D converter 509 first detects the arrival of RF analogsignals, it can time stamp the data based on time stamp signals receivedfrom the laser transceiver node 120. The time stamp is generated inlaser transceiver node 120 and transmitted to the subscriber opticalinterface 120, where it is added to the digitized RF signal by way ofcontroller 519 and data conditioner 407 (see FIG. 10 a), which adds thetime stamp to the data stream. This time stamp becomes the basis ofrecovering accurate timing at the data service hub 110. RF packets willbe transmitted in the first interstitial burst time after a delay oft_(VST) 1410 from the start of the incoming data. The arrows connectingrows 2 and 3 of FIG. 14 demonstrate when each interstitial 1300comprising the RF packets could be transmitted.

The interstitials 1300 are sent to the laser transceiver node 120, asshown in row 4 in FIG. 14. The RF packets in a respective interstitial1300 are routed via the optical tap routing device 435 to the dataconditioner 407 in FIG. 5. As noted previously, the data conditioner 407may comprise a FIFO which is a special purpose circuit known to thoseskilled in the art. The data conditioner 407 in the laser transceivernode 120 takes in the interstitial 1300 at its burst rate, and then putsout the RF data packets (“plays the RF data packets out”) at the slowerclock frequency that corresponds to the rate in which the packets passthrough the A/D converter 509 and data reducer 511 (that is, the samerate as in row 2 of FIG. 14). The data conditioner 407 of the lasertransceiver node 120 can be used to slow down the interstitial 1300 fromthe burst rate at which it was sent (500 Mb/s in one exemplaryembodiment) to the rate at which the data was accumulated (40 Mb/s inone exemplary embodiment).

The data conditioner 407 of the laser transceiver node can begin playingout the RF packets, as illustrated in Row 5 of FIG. 14, as soon as thedata conditioner 407 begins receiving the data, because it is assured ofreceiving data in at a fast enough rate that it will not run out of databefore it completes the sending of the RF packets. The reason forslowing the data rate down at the laser transceiver node 120 is toreduce the power required of the optical link between the lasertransceiver node 120 and the data service hub 110. Row 6 of FIG. 14illustrates grouping reconstructed RF packets at the adder 313 of FIG.7.

After passing through the adder 313, the RF packets can be transmittedat 1310 nm, using the same optical fiber 160 that is used to deliver thedownstream video and the downstream video service control signals. TheRF packets will arrive at the data service hub 110 as illustrated inFIG. 3, on low speed optical receiver 370. From here the RF packets aresupplied to the delay generator 305. The delay generator may alsocomprise a FIFO. Delay generator 305 may accept each RF packet in at therate that is needed in the data-to-RF converter 307, but the signal isusually further delayed in the delay generator 305 in order to be timedcorrectly. The delay is calculated from the time stamp added at thesubscriber optical interface 140, described above.

At a minimum, in one exemplary embodiment, the delay must besubstantially equal to an interstitial interval or t_(INSTL) 1430 toprevent one RF packet from getting ahead when there is RF packet justprior to it. More delay usually must be added according to how muchpropagation delay is experienced across the optical network. In oneexemplary embodiment, data being sent from laser transceiver node 120 todata service hub 110 is sped up slightly to prevent overlap of adjacentdata packets coming form two different laser transceiver nodes 120.

Referring now to FIG. 15, this figure illustrates exemplary timingdelays between respective subscriber optical interfaces 140. As notedabove, the legacy video service system will respond in the same manneras if the RF return system of the present invention were not present. Inthe example illustrated in FIG. 16 (discussed below), it is assumed thatthe video service terminals 117 (not shown) have not received theirproper timing offset to account for their distance from the data servicehub 110. That is, each video service terminal 117 (not shown) connectedto a respective subscriber optical interface 140 is not marshaled.Normally as each video service terminal 117 is added to the system, itis automatically discovered by the video service controller 115, andmarshaled at that time. Thus, in a real world example, there would notbe a number of video service terminals 117 that were out of timesimultaneously, but FIG. 15 demonstrates this unlikely scenario for thesake of illustration.

Normally, as explained in conventional standards DVS 167 and DVS 178that govern the legacy video services system, a wide or longer time slotis provided periodically to allow the discovery and marshaling of a newvideo service terminal 117, without risking the terminal 117transmitting simultaneously with a previously marshaled video serviceterminal 117. In FIG. 15, two laser transceiver nodes 120A and 120Bservice a number of attached subscriber optical interfaces 140. The twolaser transceiver nodes 120A and 120B are positioned at differentdistances from the data service hub 110, resulting in differingpropagation delays between the data service hub 110 and the two lasertransceiver nodes 120A and 120B. There are also differing propagationdelays between the two laser transceiver nodes 120A and 120B and theirappended subscriber optical interfaces 140, due to different lengths ofoptical waveguides connecting each subscriber optical interface 140 toits respective laser transceiver node 120.

In the example in FIG. 15, arbitrary time units have been used that arerelated to the graphical construct used for illustration. This does notreduce the generality of the technique to accommodate different realpropagation delays.

All of the subscriber optical interfaces 140 illustrated in FIG. 15 areconnected back to one video service control receiver 309 as illustratedin FIG. 4. Thus, the subscriber optical interfaces 140 are timed suchthat their signals will be received at the video service controlreceiver 309 (located in data service hub 110) at a scheduled time, toallow the video service control receiver 309 to marshal them just as ifthey were connected via a conventional HFC network rather than a opticalnetwork of the present invention.

FIG. 15 corresponds with two timing diagrams that are illustrated inFIGS. 16 and 17. FIG. 16 assumes that the video service terminals 117have not been timed properly with the data service hub 110. The timingdiagram of FIG. 16 will usually occur when the video service terminals117 are first installed. When video service terminals 117 respond to thevideo service control receiver 309, the receiver 309 will measureresponse time error and will instruct the video service terminal 117 toadvance its timing sufficiently to make the response be received at thevideo service control receiver 309 at the proper time. FIG. 17illustrates the situation in which all the video service terminals 117have been recognized or have been registered with the receiver 309.

Referring back to FIG. 15, the numbers adjacent to each opticalwaveguide path indicate exemplary one-way time delays between the twoends of the path. These exemplary time delays are well understood bythose skilled in the art, and relates to the propagation delay throughoptical waveguides. The first laser transceiver node 120A is locatedcloser to the data service hub 110 relative to the second lasertransceiver node 120B, so there is no significant propagation delaybetween the laser transceiver node 120A and data service hub 110. Thesecond laser transceiver node 120B is located further from the dataservice hub 110, so there are an exemplary two units of delay in theone-way optical waveguide path. Similarly, there is an exemplary 0.5unit of delay between the first laser transceiver node 120A andsubscriber optical interface 140 ₁, and two units of delay between thesecond laser transceiver node 120B and subscriber optical interface 140₄. Other delays are as shown in the FIG. 15.

Referring now to FIG. 16, this figure illustrates the situation thatexists when none of the video service terminals 117 are marshaled. Thatis, each video service terminal 117 does not know how much in advance ofthe start of a terminal time slot 1410 it is to transmit RF packets tomake up for any propagation delay. Because the video service terminals117 in this example do not have this advance information, they willtypically transmit as soon as their assigned time slot occurs. This willoften result in the RF packets arriving back at the video servicecontroller 115 too late.

The video service controller 115 will typically measure the amount oflateness or delay and send a signal to the video service terminal 117informing it how much in advance of a data slot it should transmit RFpackets. In actual implementation, usually only one video serviceterminal 117 at a time will be marshaled. As a result of theillustration of a plurality of unmarshaled video service terminals 117depicted in FIG. 16, there are data collisions at the data service hub,which will usually not exist in any actual implementation.

FIG. 16 illustrates how the video service terminal RF data packets willusually travel to the data service hub 110, using the opticalarchitecture and its associated timing delays depicted in FIG. 15. Twopackets in FIG. 16 will be described in detail below. The first packetwill be packet A(1) that travels from subscriber optical interface 140₁, through laser transceiver node 120A, to data service hub 110 andfinally to the video service control receiver 309. For packet A(1), the“(1)” indicates that it originated in the video service terminal 117(not shown) connected to subscriber optical interface 140 ₁. The “A”indicates that the subscriber optical interface 140 ₁ is connected tolaser transceiver node 120A. The second packet that will be described ispacket B(4) that passes through laser transceiver node 120B.

The video service controller 115 sends out the timing pulses 1405 asshown in row 1 of FIG. 16. Row 2 demonstrates the time at which A/Dconverter 509 and associated circuitry sends an RF packet to processor550. The timing 1420 of the RF packets are shown in two sub rows of row2 because the times will overlap

In the example described in FIG. 15, laser transceiver node 120A islocated so close to the data service hub 110 that there is nosignificant propagation delay between the two devices. Subscriberoptical interface 140, is located 0.5 time units of propagation delayfrom laser transceiver node 120A. Recall that the video service controltime marks 1405 in row 1 (of FIG. 16) are times as viewed from the dataservice hub 110. The video service terminal 117 (not shown) atsubscriber optical interface 140 ₁ transmits 0.5 time unit later thanthe first timing mark 1405(1) as a result of the 0.5 delay, as shown bythe slanted dashed line 1605 between the first timing mark 1405(1) inrow 1 and the video service terminal packet start time in row 2.

Row 3 a contains two sub rows 3 a 1 and 3 a 2. Subrow 3 a 1 depicts thetiming of interstitials 1300 of RF packet data (separated by t_(INSTL)1430) and non-video service terminal packet data 1425 bound for lasertransceiver node 120A. Subrow 3 a 2 depicts the actual interstitialburst from each subscriber optical interface 140 without illustratingany of the regular, non-video service terminal packet data. The RFpackets of row 2 are transmitted according to the rule in mentioned inFIG. 14: during the first interstitial 1300 occurring at least the videoservice terminal transmission time increment after the start of thevideo service terminal transmission. The delay from when the beginningof the RF packet A(1) arrives at the subscriber optical interface 140 ₁and when it leaves, is denoted by slanted dashed line 1610.

A delay does not exist between the time when the interstitial intervalbegins and the RF packet A(1) leaves the subscriber optical interface140 ₁, as shown by vertical line 1615. Since there is 0.5 unit ofpropagation delay from subscriber optical interface 140 ₁ and lasertransceiver node 120A (as illustrated in FIG. 15), the time the RFpacket A(1) arrives at the laser transceiver node 120A is delayed by 0.5unit, as shown by dashed line 1620, which is slightly slanted.

In row 5 a, as soon as the RF packet A(1) arrives at the lasertransceiver node 120A, it is slowed by data conditioner 407, and startsbeing played out at the same data rate as in row 2. When RF packet A(2)arrives, its playout must be delayed because RF packet A(1) has notfinished playout at that time. Usually this does not cause a problem,since RF packet A(2) simply “gets in line” in the data conditioner 407behind RF packet A(1) and begins playing out RF packet A(2) when theplaying out of RF packet A(1) is completed.

RF packet A(1) arrives at the data service hub 110 (row 6 a) withoutdelay, by virtue of little separation between data service hub 110 andlaser transceiver node 120A. This is shown with vertical line 1625. Atthe data service hub, the delay generator 305 reads the timestamp thatwas attached to the RF packet at the subscriber optical interface 140,and delays the data for the total time programmed, which depends on thetotal propagation delay 1630 from the furthest subscriber opticalinterface to the data service hub. The total propagation delay parameterdelta t 1630 is supplied at system set-up. Delta t 1630 is illustratedat the bottom of FIG. 16. The point from which delta t 1630 is measuredis shown at packet A(11) in row 2 of FIG. 16, as an example.

The tracking of packet B(4) will now be described. Packet B(4) istracked as it moves from subscriber optical interface 140 ₄ to the dataservice hub 110. Propagation delay to subscriber optical interface 140 ₄is a total of four units (see FIG. 15). Two units of one-way delay existbetween the data service hub 110 and the laser transceiver node 120B.Another two units of delay exist between the laser transceiver node 120Band subscriber optical interface 140 ₄. Because of this delay, the timethat the RF packet B(4) of FIG. 16 is transmitted is delayed by fourunits as shown by diagonal line 1635. Row 3 b 1 shows RF packet timingfor the subscriber optical interfaces attached to laser transceiver node120B. RF packet B(4) usually must wait for the interstitial burst timeshown, so it is transmitted with a delay represented by slanted line1640.

There is another delay of two units from subscriber optical interface140 ₄ to laser transceiver node 120B, represented by slanted dashed line1645. At row 4 b in FIG. 16, the burst RF packet B(4) arrives at thelaser transceiver node 120 _(B), where it immediately begins gettingplayed out at the speed of row 2. This RF packet B(4) is transmittedback to the data service hub 110, but encounters a propagation delay oftwo units along the way, so it arrives at the data service hub 110delayed by 2, as shown by slanted dashed line 1650. Finally, RF packetB(4) is delayed by a total of delta t 1630 as measured from thebeginning of the packet start in row 2, which is the time that wastime-stamped at the subscriber optical interface.

Row 8 of FIG. 16 indicates the amounts by which the video servicecontroller 115 must tell each video service terminal 117 to advance itstransmission in order to get its RF packet data back to the data servicehub 110 at the correct time the nearest video controller system timemark of row 1. This correction time is unique for every video serviceterminal, and may be measured from the time mark at which the data areexpected to the time the data arrives, and is shown for packet A(2)below row 8 packet A(2) at 1655. This time is usually transmitted to thevideo service terminal 117, which then advances its transmission time bythat amount.

A number of collisions are shown in row 7 of FIG. 16 represented by RFpackets that overlap each other in time. The RF packets are separatedvertically simply to allow the reader to see them individually. Thecollisions can be resolved by marshaling the video service terminals117. Marshaling can be defined as the transmission of the timingcorrections of row 8 to the video service terminals 117.

FIG. 17 illustrates how the video service terminal RF data packets willusually travel to the data service hub 110, using the opticalarchitecture and its associated timing delays depicted in FIG. 15.However, unlike FIG. 16, FIG. 17 illustrates video service terminals 117that have been marshaled by the video service controller 115 tocompensate for the timing delays depicted in FIG. 15. Only thedifferences between FIGS. 16 and 17 will be described below.

Compared to FIG. 16, the subscriber optical interface timing in rows 3 a1 and 3 b 1 of FIG. 17 have been changed. Since the legacy video servicesystem and the present invention have completely independent timingdomains, the timing between the two different systems will typicallyslip. The timing of FIG. 17 may be followed as in FIG. 16, with the samelines marked to show timing relationships. The difference in FIG. 17 isthat when the RF packets reach the data service hub 110 they are in theproper timing relationship as illustrated in row 7 of FIG. 17.

The minimum delay time delta t 1630 that the system should introduce canbe calculated by the following equation:Δt=t _(VST) +t _(INSTL) +t _(prop) +t _(residual), where

-   -   Δt=delay time from when an interstitial burst is first seen at        subscriber optical interface 140 to when it is presented to the        video service controller 115 at the data service hub 110.    -   ^(t)VST=minimum time between which two different video service        terminals 117 can transmit upstream RF packet data (see FIG.        14).    -   ^(t)INSTL=interstitial time in the RF return system (see FIG.        14).    -   ^(t)prop=difference in one-way propagation time in longest and        shortest total length of an optical waveguide to be used.    -   ^(t)residual=any residual delays in A/D 509, D/A 524, data        conditioners 407, and other circuitry in the RF return path.

Failure to introduce delta t 1630 will usually require some packets tobe played out at the data service hub 110 before they are available. Inthe example above, t_(VST)=7, t_(INSTL)=5, t_(PROP)=4, andt_(RESIDUAL)=0. In this case delta t 1630 will typically equal sixteenat a minimum. The value of delta t 1630 used in the graphical solutionsof FIGS. 16 and 17 was seventeen, one more time unit than is necessary.In FIG. 17, rows 6(B) and 7, RF packet B(7) usually must play out onlyone unit after the leading portion of it becomes available. This oneunit is the additional delta t 1630 over and above the minimum. Haddelta t 1630 been less than sixteen, then the RF packet B(7) would bedemanded before it was available.

Delta t 1630 may be understood as follows. The delay of t_(VST) comesfrom the requirement to delay the data transmission from the subscriberoptical interface 140 until after a complete RF packet of data isavailable. This is necessary to ensure that a complete RF packet isavailable when the system is ready to transmit it, and to ensure thattwo packets from different video service terminals 117 don't collide.The t_(INSTL) delay 1430 is added because once the RF packet (row 2) isready, it may have to wait this long before an interstitial intervalcomes along. A delay of t_(PROP) is needed to allow the signal topropagate from the subscriber optical interface 140 to the data servicehub 110. The t_(RESIDUAL) time accounts for any unavoidable processingdelay in digitizing and data reducing the RF signal or changing it backto the original analog RF form, plus residual delay in the two dataconditioners 407 in the signal chain (in the subscriber opticalinterface 140 and laser transceiver node 120), plus any other smalldelays.

In addition, note that the video service controller 115 will usually berequired to allow for an extra integer number of delay increments oft_(VST) 1410 as a result of the introduction of the RF return system ofthe present invention. The number of t_(VST) 1410 increments requiredcan be calculated as follows:

$I\; N\;{{T( \frac{\Delta\; t}{t_{V\; S\; T}} )}.}$INT indicates that the integer portion of the argument is to be taken.In the example case above, delta t=17 and t_(VST)=7. Therefore thenumber of increments of t_(VST) that the video service controller 115must usually allow for is equal to two, consistent with the way FIGS. 16and 17 are depicted.

The aforementioned exemplary embodiments are typically used in themajority of cases in which the service provider of an opticalarchitecture wants to provide video services and data services. However,in some cases, some or all of the subscribers may only want to subscribeto video services. Where only video services are desired by subscribers,there are lower cost methods to provide support for a RF return channelthat does not include all of the data circuitry required to support dataservices. In these cases, it is also possible that the service providermay want to support a return channel for modem data as well as videoservice terminal data. These additional requirements may be accommodatedby the various alternative embodiments as discussed below.

Referring now to FIG. 18, this figure illustrates the situation where asubscriber is not using any data services, but data services are beingsupplied to other subscribers. The approach taken in this case is tomodulate the return RF signal from the video service terminal 117 ontoan inexpensive Amplitude Modulated (AM-analog) optical transmitter 530′used to transport only the video service terminal return signal. Becauseit transports only one signal at a time, and because that signalcontains only simple forms of digital modulation, the quality of the AMoptical transmitter 530′ can be low. Also, much of the RF returnprocessing circuitry can be placed in the laser transceiver node 120 toservice multiple subscriber optical interfaces 140.

The wavelength emitted by AM optical transmitter 530′ usually must notbe in the 1310 nm region because other users may be using datatransported at this wavelength as shown in the first sections of thisdisclosure. Suitable wavelengths for lambda λ₃ include 1490 nm ±10 nm,which is being used for some specialized applications, other wavelengthsin the vicinity of 1550 nm not being used by the analog opticaltransmission path, and 1625 nm which is sometimes used for internalcommunications within optical networks. However, the present inventionis not limited to these wavelength regions and can include regionshigher or lower than described with out departing from the scope andspirit of the present invention. As VCSEL (vertical cavity surfaceemitting laser) devices come into common use, it is expected that theywill make particularly advantageous transmitters for this application,although other technologies may be used.

It is important to turn off transmitter 530′ when data is not beingtransmitted, because other subscriber optical interfaces may betransmitting when this one is not. RF presence detector line 372 detectsthe existence of RF data and turns on transmitter 530′.

The return RF optical signal is diplexed onto fiber 150 and transportedto the laser transceiver node 120 as shown previously. As discussedabove, optical waveguide 150 serves a plurality of subscribers, all ofwhose signals will be combined before arriving at triplexer 420′₁. Atlaser transceiver node 120, the signal at wavelength λ₃ (lambda 3) isseparated in triplexer 420′₁. This device works the same as thepreviously-introduced diplexer 420′₁, except that a third output hasbeen added, at a wavelength of lambda λ₃. Such triplexers 420′₁ areknown to those skilled in the art.

As shown in FIGS. 6 and 7 above, a plurality of input/output ports 445exist at the laser transceiver node 120, and each may have need of theinstant teaching. Thus, the lambda λ₃ outputs of all triplexers 420′₁are combined in optical combiner 320.

From optical combiner 320, the optical signal is supplied to AM opticalreceiver 370′, which converts the optical signal(s) from the subscriberoptical interface(s) 140 back to electrical form. At this point, thesignal is the same as that applied to the input of A/D converter 509 inFIG. 8, though there may be a plurality of signals if more than onesubscriber is using this return method. RF return signals will usuallynot overlap in time, because the video service controller 115 managesthe video service terminals 117 to prevent an overlap.

The function of A/D converter 509, data reducer 511, and dataconditioner 407 is identical to that of the corresponding parts in FIG.8 and other figures, with the exception that the RF signal does not needto be sped up into an interstitial burst as was required previously fortransmission to the laser transceiver node 120. The purpose of theaforementioned interstitial burst where the data conditioner 407 in thesubscriber optical interface 120 increased the transmission rate of thereturn RF packet was to transmit the RF packet to the laser transceivernode 120 without interfering with other regular data packets, bycondensing its time and bursting it out between other regular non-videoservice data packets. Developing the interstitial burst is not necessaryin FIG. 18 for the RF data being digitized in the laser transceiver node120 because by the time the signal has reached the laser transceivernode 120, the RF data packets are separated from the other data packetsanyway. No interstitial transmission is needed in this exemplaryembodiment. However, data conditioner 407 for the RF data being emittedfrom subscribers who also produce regular data packets operatesidentically as in FIG. 6, meaning that the data conditioner 407 forthese subscribers who have data services does slow down the RF packetsat this stage.

The optical signal present line 372 is used to suppress A/D conversionwhen no signals are present. That is, it can preclude noise from causingspurious counts from the A/D converter 509. The data conditioner 407operating on data coming through AM optical receiver 370′ (unlike thedata conditioner 407 above it) doesn't need to take in data at theinterstitial burst rate and slow it down, but it does need to delay thedata as shown between rows 2 and 5 of FIGS. 16 and 17. Finally adder 313is used to combine the signals from the two data conditioners 407. Thecombined RF signal is transmitted upstream using transmitter 325. Sinceother signals can be combined with this one upstream signal, it may bemore energy efficient to turn on the transmitter 325 only when there issomething to transmit. This may be accomplished with the two dataconditioners 407 being coupled to an OR gate 421 where the resultingsignals are used to turn on transmitter 325.

Operation of the data service hub 110 (not shown) that is connected tothis laser transceiver node 120 in FIG. 18 is identical to thatillustrated in FIG. 3. The RF packets arriving back at the data servicehub 110 (not shown) are identical with those described with respect toFIG. 3.

Referring now to FIG. 19, this figure illustrates the situation wheredata services are not provided to any subscriber. Because of thesimilarities between FIGS. 18 and 19, only the differences between thesetwo figures will be described.

As it is apparent from FIG. 19, the equipment at the laser transceivernode 120 associated with other upstream data delivery has beeneliminated. Also, the wavelength of AM optical transmitter 530 has beenchanged back to 1310 nm. The operation could take place on theaforementioned lambda λ₃ wavelength, but using 1310 nm will likelyresult in cost savings. However, other wavelengths or wavelength regionscould be used without departing from the scope and spirit of the presentinvention. Triplexer 420′₁ of FIG. 18 has now been replaced with adiplexer in FIG. 19.

The activation of the optical transmitters 530′ and 325 is accomplishedin a similar manner as described in FIG. 18. The RF packets arrivingback at the data service hub 110 (not shown) is identical with that ofthe FIG. 3 system.

Referring now to FIG. 20, this figure illustrates the situation wheredata services are not provided to any subscriber and RF packets are notused. Rather, the signals stay in RF-modulated form and are notconverted to digital packets. But because there are still similaritiesbetween FIGS. 19 and 20, only the differences between these two figureswill be described.

FIG. 20 illustrates an exemplary embodiment that is well suited forshort distances. In this exemplary embodiment, costs can be lowered ifRF data is returned all the way to the data service hub 110 as RFsignals modulated onto analog lasers. Since only one signal is usuallypresent at a time by virtue of the way the legacy video service systemworks, the quality of the transmitters can be low.

The subscriber optical interface 140 of FIG. 20 is identical with FIG.19, but the laser transceiver node 120 is different. In this case allreturn RF optical signals from all subscriber optical interfaces 140,coming from different input/output ports 445 are combined in an opticalcombiner 320. Since the RF optical signals are typically transmitted ata wavelength of 1310 nm, they cannot be economically amplified, so theyare converted to electrical form in AM optical receiver 370, thenreconverted to optical form in AM transmitter 325. The optical signalpresent line 372 is used to turn on AM transmitter 325, so that opticalnoise received when signals are not present, will not propagate upstreamfrom the laser transceiver node 120.

As solid state amplifiers operative at 1310 nm become widely availableand operate in the requisite temperature environment, a solid stateamplifier 333 can replace AM optical receiver 370 and AM transmitter325.

In FIGS. 18, 19, and 20, the single AM optical receiver 370 may bereplaced my a plurality of AM optical receivers 370, each just after itsrespective diplexer 420 ₁. And optical combiner 320 can be replaced withan RF combiner. This would accommodate lower loss budgets because theoptical signal would not suffer the loss of optical combiner 320. On theother hand, it would drastically increase the number of AM opticalreceivers 370 required.

As noted above, the exemplary embodiments described in FIGS. 1–9 can beused to address all the needs of subscribers in which the data serviceprovider of a FTTH or similar system wants to provide for subscribervideo service and data service. However, as mentioned in connection withFIGS. 18–20, in some cases subscribers will only want video service.Where only video service is wanted, there are lower cost ways to providesupport for a return RF channel, rather than to include all the datacircuitry required to support both data packets and RF packets. In thesescenarios where only video services are desired, it is also possiblethat the data service provider will want to support a return channel formodem data as well as video service terminal data. These additionalrequirements may be accommodated by the various alternative embodimentsillustrated in FIGS. 18, 19, and 20.

FIG. 21 illustrates a method 2100 to determine which RF return method ofthe methods previously described to use in a particular situation.Certain steps in the process described below must naturally precedeothers for the present invention to function as described. However, thepresent invention is not limited to the order of the steps described ifsuch order or sequence does not alter the functionality of the presentinvention. That is, it is recognized that some steps may be performedbefore or after other steps without departing from the scope and spiritof the present invention.

The method 2100 starts with step 2105 when a subscriber needs RF returnsupport for either a video service terminal 117 and/or a cable modem(not shown). In decision step 2110, it is determined whether or not theFTTH system offers data services to any subscribers. This is importantbecause if the system does offer data services to other subscribers,then even if the subject subscriber does not take data services, thereare limitations on what can be done to the return RF data so as to notinterfere with data being taken by other subscribers.

If the inquiry to decision step 2110 is positive, then the “Yes” branchis followed decision step 2115 in which it is determined whether aparticular subscriber has data service in addition to needing RF returnsupport. If the inquiry to decision step 2110 is negative, the “No”branch is followed to decision step 2120 in which it is determined ifthe RF return signals will be propagated over relatively short distancesas perceived from an optical waveguide/power design perspective.

If the inquiry to decision step 2115 is positive, then the “Yes” branchcan be followed to step 2125 in which the exemplary embodimentillustrated and summarized in FIG. 9 should be selected to address theneeds of the subscribers. If the inquiry to decision step 2115 isnegative, then the “No” branch can be followed to step 2130 in which theexemplary embodiment illustrated in FIG. 18 should be selected toaddress the needs of the subscribers

If the inquiry to decision step 2120 is negative, then the “No” branchcan be followed to step 2135 in which the exemplary embodimentillustrated in FIG. 19 should be selected to address the needs of thesubscribers. If the inquiry to decision step 2120 is positive, then the“Yes” branch can be followed to step 2140 in which the exemplaryembodiment illustrated in FIG. 20 should be selected to address theneeds of the subscribers.

Referring now to FIG. 22, this figure illustrates an exemplary methodfor returning video service RF signals in an upstream direction.Basically, FIG. 22 provides an overview of the processing performed bythe subscriber optical interfaces 140, laser transceiver nodes 120, anddata service hub 110.

As noted above, certain steps in the process described below mustnaturally precede others for the present invention to function asdescribed. However, the present invention is not limited to the order ofthe steps described if such order or sequence does not alter thefunctionality of the present invention. That is, it is recognized thatsome steps may be performed before or after other steps withoutdeparting from the scope and spirit of the present invention.

Step 2205 is the first step in the exemplary upstream overview process2200. In step 2205, terminal input is received at a video serviceterminal 117. Next, in step 2210, the terminal input is propagated asmodulated analog RF signals towards the subscriber optical interface140.

In step 2215, the analog RF signals are converted to digital packetswith the A/D converter 509. However, it is noted that step 2215 does notneed to take place in the subscriber optical interface 140. As discussedabove, the analog to digital conversion process can take place at thelaser transceiver node 120 or it could occur at the video serviceterminal 117.

Next, in routine 2220, the size of the RF packets generated by the A/Dconverter 509 are reduced by the data reducer 511. Further details ofroutine 2220 have been described above with respect to FIG. 10D.

In step 2225 time-stamped data is added to the reduced RF packets. Instep 2230, identification information is added to the reduced RF packet.This identification information can comprise headers used to uniquelyidentify RF packets from other types of data packets. Steps 2225 and2230 can be performed by a data condition 407. However, functionsidentified in steps 2230 and 2235 can be accomplished with otherhardware devices other than the data conditioners 407. The presentinvention is not limited to the hardware devices which performs thefunctions described in steps 2230 and 2235 nor is the present inventionlimited to the order in which these two steps are performed.

In routine 2240, the reduced RF packets are combined with regular datapackets. Further details of routine 2240 will be discussed below withrespect to FIG. 23.

In step 2245, the electrical packets are converted to the opticaldomain. Next, in step 2250, the combined optical packets are propagatedtowards the laser transceiver node 120.

In step 2255, the combined optical packets are converted to theelectrical domain with a digital optical receiver such as the receiver370 as illustrated in FIG. 5. In step 2270, the reduced RF packets areseparated from the regular data packets in the optical tap routingdevice 435 of the laser transceiver node 120.

The transmission speed of the reduced RF packets is then decreased bythe data conditioner 407 in the laser transceiver node 120 (step 2275).Next, in step 2280, the reduced RF packets are converted back to theoptical domain by a low power optical transmitter 325.

In step 2285, the reduced RF packets are propagated upstream towards adata service hub 110 along an optical wave guide 160 that also carriesdown stream video signals and video service control signals. In step2288 the reduced RF Digital packets are converted back to the electricaldomain in low speed data receiver 370. In step 2290, the RF Digitalpackets are delayed to their proper playout time in delay generator 305.

In routine 2295, the reduced RF packets are converted to the original RFanalog signals that were originally produced by the video serviceterminals 117. Further details of routine 2295 have been described abovewith respect to FIG. 11 b. In step 2298, the RF analog signals arepropagated to the RF receiver 309 that is coupled to the video servicescontroller 115.

Refer now to FIG. 23, this figure illustrates an exemplary subroutine orsubprocess 2240 for combining reduced RF packets with regular datapackets as discussed above with respect to FIG. 22.

The combining reduced RF packets with regular data packets routine 2240,starts with step 2305. In step 2305, the regular data transmission ofordinary data packets produced by the processor 550 in FIG. 8 isinterrupted during predetermined intervals. As noted above, while theupstream transmission of data packets can be interrupted at intervalswith upstream RF packet transmission, it is noted that the intervals ofinterruption do not need to be regularly spaced from one another intime. However, in one exemplary embodiment, the interruptions can bedesigned to be spaced at regular, uniform intervals from one another. Inanother exemplary embodiment (not shown), the interruptions could bespaced at irregular, non-uniform intervals from one another. In step2310, reduced RF packets are inserted between irregular data packets ifthe RF packets are available during an interval.

Step 2310 corresponds to the simultaneous activation of switches 513 ineach subscriber optical interface 140 that is part of a subscribergrouping. The subscriber groupings are usually determined by the numberof subscribers that will be serviced by a particular video servicereceiver 309 that is typically located in the data service hub 110.After step 2310, the subprocess ends and the process returns to step2245, FIG. 22.

Refer now to FIG. 24, this Figure illustrates an exemplary method forpropagating downstream analog video service control signals within anoptical architecture. The downstream process 2400 starts in first step2405. In step 2405, analog electrical video service control signals arereceived from a video service controller 115. Next, in step 2410, theanalog electrical video service control signals are combined with analogdownstream video signals.

In step 2415, the analog electrical video service control signals andvideo signals are converted to the optical domain with an opticaltransmitter 325. The combined video optical signals are propagatedtowards laser transceiver nodes 120 via optical wave guides 160. In step2425, the combined video optical signals are also combined with dataoptical signals in the laser transceiver node 120. Specifically, in anexemplary embodiment of the present invention, the video optical signalscan be combined with the data optical signals in a diplexer 420 Thecombined video and data optical signals are propagated along an opticalwave guide 150 to a subscriber optical interface 120. In step 2435, thevideo optical signals are separated from the data optical signals withan optical diplexer 515. The video optical signals are then converted tothe electrical domain with an analog optical receiver 525.

In step 2445, the video service control signals are separated from theregular video signals in the video services terminal 117. Next, in step2450, the video service control signals are processed by the videoservice terminal 117.

The present invention is not limited to the aforementioned lasertransceiver nodes. The present invention may employ nodes that operatewith LEDs that produce wavelengths that may be unique to subscribers orgroups of subscribers. In other words, each node can further compriseone or more wavelength division multiplexers and demultiplexers. Eachwavelength division multiplexer (WDM) can select one or more wavelengthsof optical bandwidth originating from a respective optical tapmultiplexer. Each WDM can then combine the one or more wavelengths ofoptical bandwidth together and feed them into a single opticalwaveguide. In this way, one optical waveguide can service a number ofindividual optical taps that can correspond to the number of optical tapmultiplexers present in the bandwidth transforming node. In such anexemplary embodiment, each optical tap can divide data signals between aplurality of subscribers and can be capable of managing optical signalsof multiple wavelengths.

The present invention is not limited to providing a return path for justlegacy video service terminals. The return path of the present inventioncan be carry signals of other hardware devices that may notcharacterized as “legacy” hardware. The present invention may simply beused to provide increased bandwidth for additional conventionalelectronic communication devices that are supported by the opticalnetwork.

Thus, the present invention provides a unique method for inserting RFpackets (derived from RF signals produced by a terminal) betweenupstream packets comprising data generated by a subscriber with adigital communication device such as a computer or internet telephone.Thus, the present invention provides an RF return path for legacyterminals that shares a return path for regular data packets in anoptical network architecture. The present invention also provides a wayin which the upstream transmission timing scheme that is controlled bythe legacy video service controller housed within the data service hubis preserved. The present invention can operate independently of thelegacy upstream transmission timing scheme so that the legacy upstreamtransmission timing scheme can remain effective. The present inventioncan also adjust the transmission rate of RF packets during certainstages in an optical network in order to take advantage of lower costhardware.

In another alternative exemplary embodiments, the present inventionallows for less complex hardware that can be provided in the subscriberoptical interface or laser transceiver node or both for subscribers thatare not taking data services.

In other alternative exemplary embodiments, an optical signal presentline in combination with a driver may be employed in order to reduce theamount or cost of hardware (or both) in a laser transceiver node.

It should be understood that the foregoing relates only to illustratethe embodiments of the present invention, and that numerous changes maybe made therein without departing from the scope and spirit of theinvention as defined by the following claims.

1. A return path of an optical network system comprising: a data servicehub for processing upstream radio-frequency analog video service controlsignals and generating downstream radio-frequency analog video servicecontrol signals according to a first timing scheme, the data service hubcomprising a data-to-radio-frequency converter for receiving upstreamdigital data signals comprising upstream radio-frequency video servicecontrol signals and a time stamp that preserves the first timing schemeand that initiates recovery of the upstream radio-frequency analog videoservice control signals by the converter from the upstream disital datasignals; at least one subscriber optical interface for receiving theupstream radio-frequency analog video service control signals, forconverting the upstream radio-frequency analog video service controlsignals to first digital packets and combining the first packets withsecond packets in a time domain for upstream transmission towards thedata service hub, for preserving the first timing scheme between theupstream and downstream video service control signals, the subscriberoptical interface further comprising an analog-to-digital converter forconverting the upstream radio-frequency analog video service controlsignals into digital data signals prior to first packet formation andfor adding the time stamp to the digital data signals that preserves thefirst timing scheme of the video service control signals of the dataservice hub; and one or more optical waveguides connected to thesubscriber optical interface, for carrying the upstream optical signalsand downstream optical signals that are propagated according to a secondtiming scheme independent of the first timing scheme.
 2. The return pathof claim 1, further comprising a laser transceiver node forcommunicating optical signals to the data service hub, and forapportioning bandwidth between subscribers of the optical networksystem.
 3. The return path of claim 1, wherein the second packetscomprise data other than the upstream radio-frequency analog videoservice control signals.
 4. The return path of claim 1, wherein thesubscriber optical interface further reduces a size of the firstpackets.
 5. The return path of claim 1, wherein the subscriber opticalinterface comprises a data reducer for adjusting a size of the firstpackets.
 6. The return path of claim 1, wherein the subscriber opticalinterface comprises a data conditioner for increasing a transmissionspeed of the first packets.
 7. The return path of claim 6, wherein thedata conditioner comprises a FIFO buffer.
 8. The return path of claim 1,wherein the subscriber optical interface comprises a processor foradministering a timing of when the first and second packets arecombined.
 9. The return path of claim 2, wherein the laser transceivernode coordinates timing among a plurality of subscriber opticalinterfaces.
 10. The return path of claim 1, further comprising anoptical tap coupled to the subscriber optical interface.
 11. The returnpath of claim 1, further comprising a terminal for producing theupstream radio-frequency analog video service control signals andcoupled to the subscriber optical interface.
 12. A return path of anoptical network system comprising: a data service hub for processingupstream radio-frequency analog video service control signals andgenerating downstream radio-frequency video service control signalsaccording to a first timing scheme, the data service hub comprising adata-to-radio-frequency converter for receiving upstream digital datasignals comprising a time stamp that preserves the first timing schemeand that initiates recovery of the upstream radio-frequency analog videoservice control signals by the converter from the upstream digital datasignals; at least one subscriber optical interface for receiving theupstream radio-frequency analog video service control signals, forconverting the upstream radio-frequency analog video service controlsignals to first digital packets and combining the first packets withsecond packets in a time domain for upstream transmission towards thedata service hub, for preserving the timing scheme between the upstreamand downstream video service control signals, the subscriber opticalinterface further comprising an analog-to-digital converter forconverting the upstream radio-frequency analog video service controlsignals into digital data signals prior to first packet formation andfor adding the time stamp to the digital data signals that preserves thefirst timing scheme of the video service control signals of the dataservice hub; and a laser transceiver node for communicating opticalsignals to the data service hub, and for apportioning bandwidth betweensubscribers of the optical network system; and one or more opticalwaveguides connected to the laser transceiver node, for carrying theupstream optical signals and downstream optical signals that arepropagated according to a second timing scheme independent of the firsttiming scheme.
 13. The return path of claim 12, wherein the secondpackets comprise data other than the upstream radio-frequency analogvideo service control signals.
 14. The return path of claim 12, whereinthe laser transceiver node further reduces a size of the first packets.15. The return path of claim 12, wherein the laser transceiver nodecomprises a data reducer for adjusting a size of the first packets. 16.The return path of claim 12, wherein the laser transceiver nodecomprises a data conditioner for increasing a transmission speed of thefirst packets.
 17. The return path of claim 12, wherein the dataconditioner comprises a FIFO buffer.
 18. The return path of claim 12,further comprising an optical tap coupled to the subscriber opticalinterface.
 19. The return path of claim 12, further comprising aterminal for producing the upstream radio-frequency analog video servicecontrol signals and coupled to the subscriber optical interface.
 20. Areturn path of an optical network system comprising; a data service hubfor processing upstream video service control signals and generatingdownstream video radio-frequency analog service control signalsaccording to a first timing scheme, the data service hub comprising adata-to-radio-frequency converter for receiving upstream digital datasignals comprising a time stamp that preserves the first timing schemeand that initiates recovery of radio-frequency analog video servicecontrol signals by the converter from the upstream digital data signals;at least one subscriber optical interface for receiving upstreamelectrical radio-frequency analog video service control signals, thesubscriber optical interface converting the upstream radio-frequencyanalog video service control signals to digital electrical data firstpackets and for converting the digital electrical first data packets tooptical data packets, for combining the first packets with secondpackets in a time domain and in a electrical domain for upstreamtransmission towards the data service hub, for preserving the firsttiming scheme between the upstream and downstream video service controlsignals, the subscriber optical interface further comprising ananalog-to-digital converter for converting the upstream radio-frequencyanalog video service control signals into digital data signals prior tofirst packet formation and for adding the time stamp to the digital datasignals that preserves the first timing scheme of the video servicecontrol signals of the data service hub; a laser transceiver node forcommunicating optical signals to the data service hub, for apportioningbandwidth between subscribers of the optical network system; and one ormore optical waveguides connected to the laser transceiver node, forcarrying the upstream optical signals and downstream optical signalsthat propagated according to a second timing scheme independent of thefirst timing scheme.
 21. The return path of claim 20, wherein the lasertransceiver node amplifies the optical data packets by converting themto electrical data packets and then reconverting the electrical datapackets back to optical data packets.
 22. The return path of claim 20,wherein the laser transceiver node amplifies the optical data packetswith a solid state optical amplifier.
 23. A method for providing areturn path for signals in an optical network system comprising thesteps of; generating downstream radio-frequency analog video servicecontrol signals and receiving upstream radio-frequency analog videoservice control signals according to a first timing scheme; convertingthe upstream radio-frequency analog signals to a plurality of firstdigital information packets; receiving a plurality of second digitalinformation packets; preserving the first timing scheme between theupstream and downstream video service control signals by transmittingboth sets of information packets by inserting the first digitalinformation packets between the second digital information packets in atime domain; propagating the packets towards a data service hubaccording to a second timing scheme independent of the first timingscheme; receiving the first and second digital information packets atthe data service tub; detecting a time stamp in the first digitalinformation packets with a data-to-radio-frequency converter of the dataservice hub; and initiating recovery of the upstream radio-frequencysignals from the first digital information packets with thedata-to-radio-frequency converter in response to detecting the timestamp, the time stamp preserving the first timing scheme.
 24. The methodof claim 23, further comprising the step of converting the first digitalinformation packets back to upstream radio-frequency analog videoservice control signals.
 25. The method of claim 23, wherein the step ofreceiving the plurality of second digital information packets, furthercomprises receiving the plurality of second digital information packetsfrom one of a computer and an internet telephone.
 26. The method ofclaim 23, wherein the step of receiving a plurality of second digitalinformation packets, further comprises receiving a plurality of seconddigital information packets having irregular sizes.
 27. The method ofclaim 23, wherein the step of converting the upstream radio-frequencyanalog video service control signals further comprises converting theupstream radio-frequency analog video service control signals to aplurality of first digital information packets having a uniform lengthof time slot for their transmission.
 28. The method of claim 23, furthercomprising the steps of: controlling a first time scheme with a firstcontroller for the reception of the upstream radio-frequency analogvideo service control signals; and controlling a second timing schemewith a second controller for transmission of the first and seconddigital information packets, the second controller operatingindependently of the first controller.
 29. The method of claim 23,further comprising the step of preserving the first timing scheme withthe second timing scheme by sizing transmission intervals of the secondtiming scheme such that the transmission intervals are smaller thanreception intervals of the first timing scheme.
 30. The method of claim23, wherein the step of transmitting further comprises inserting thefirst digital information packets between the second digital informationpackets during uniformly spaced intervals.
 31. The method of claim 23,further comprising the step of increasing a propagation speed of thefist digital information packets prior to the step of transmitting bothsets of information.
 32. The method of claim 23, further comprising thestep of further comprising the step of decreasing a propagation speed ofthe first digital information packets prior to the step of receiving thefirst digital information packets at a data service hub.
 33. An opticalnetwork system comprising: a data service hub for processing upstreamradio-frequency analog video service control signals and generatingdownstream radio-frequency analog video service control signalsaccording to a first timing scheme, the data service hub comprising adata-to-radio-frequency converter for receiving upstream digital datasignals comprising a time stamp that preserves the timing scheme andpath initiates recovery of the upstream radio-frequency analog videoservice control signals by the converter from the upstream digital datasignals; at least one subscriber optical interface, for receiving theupstream radio-frequency analog video service control signals, forconverting the radio-frequency analog video service control signals tofirst digital packets and combining the first packets with secondpackets in a time domain for upstream transmission towards the dataservice hub, for preserving the first timing scheme between the upstreamand downstream video service control signals, the subscriber opticalinterface further comprising an analog-to-digital converter forconverting the upstream radio-frequency analog video service controlsignals into digital data signals prior to first packet formation andfor adding the time stamp to the digital data signals that preserves thefirst timing scheme of the video service control signals of the dataservice hub; a laser transceiver node for communicating optical signalsbetween the data service hub and the subscriber optical interface andfor apportioning bandwidth between subscribers of the optical networksystem, the laser transceiver node further comprising two or moreoptical receivers that share a tap multiplexer; and one or more opticalwaveguides connected to the laser transceiver node, for carrying theupstream optical signals and downstream optical signals that arepropagated according to a second timing scheme independent of the firsttiming scheme.
 34. The optical network system of claim 33, wherein eachoptical receiver further comprises an optical signal detector fordetecting optical signals.
 35. A method for providing a return path forsignals in an optical network system comprising the steps of: generatingdownstream radio-frequency analog video service control signals andreceiving upstream radio-frequency analog video service control signalsaccording to a first timing scheme; converting the upstreamradio-frequency analog video service control signals to a plurality offirst digital information packets; receiving a plurality of seconddigital information packets; preserving the first timing scheme betweenthe upstream and downstream video service control signals by positioningthe first digital information packets between the second digitalinformation packets to form a continuous information stream in a timedomain; propagating the information stream along an optical waveguidetowards a data service hub according to a second time scheme; detectinga time stamp in the first digital information packets with adata-to-radio-frequency converter of the data service hub, the timestamp preserving the first timing scheme; and initiating recovery of theupstream radio-frequency analog video service control signals from thefirst digital information packets with the data-to-radio-frequencyconverter in response to detecting the time stamp.
 36. The method ofclaim 35, further comprising the step of converting the first digitalinformation packets back to upstream radio-frequency analog videoservice control signals.
 37. The method of claim 35, wherein the step ofreceiving the plurality of second digital information packets, furthercomprises receiving the plurality of second digital information packetsfrom one of a computer and an internet telephone.
 38. The method ofclaim 35, further comprising the step of forming the upstreamradio-frequency analog video service control signals in response tocommands inputted into a video services terminal.
 39. A return path ofan optical network system comprising: a data service hub for processingupstream radio-frequency analog video service control signals andgenerating downstream radio-frequency analog video service controlsignals according to a first timing scheme, the data service hubcomprising a data-to-radio-frequency converter for receiving upstreamdigital data signals comprising a time stamp that preserves the firsttiming scheme and that initiates recovery of upstream radio-frequencyanalog video service control signals by the converter from the upstreamdigital data signals; at least one subscriber optical interface forreceiving the upstream radio-frequency analog video service controlsignals, for converting the the upstream radio-frequency analog videoservice control signals to first digital packets for upstreamtransmission as optical signals towards the data service hub, andcombining the first packets with second packets in a time domain priorto upstream transmission, for preserving the first timing scheme betweenthe upstream and downstream video service control signals, thesubscriber optical interface further comprising an analog-to-digitalconverter for converting the upstream radio-frequency analog videoservice control signals into digital data signals prior to first packetformation and for adding the time stamp to the digital data signals thatpreserves the first timing scheme of the video service control signalsof the data service hub; and one or more optical waveguides connected tothe subscriber optical interface, for carrying the upstream opticalsignals that are propagated according to a second timing schemeindependent of the first timing scheme.
 40. The return path of claim 39,wherein the subscriber optical interface further reduces a size of thepackets.
 41. The return path of claim 39, wherein the subscriber opticalinterface comprises a data reducer for adjusting a size of the packets.42. The return path of claim 39, wherein the subscriber opticalinterface comprises a data conditioner for increasing a transmissionspeed of the digital packets.
 43. The return path of claim 42, whereinthe data conditioner comprises a FIFO buffer.
 44. The return path ofclaim 39, wherein the subscriber optical interface detects a presence ofan RF signal destined for the data service hub.
 45. A return path of anoptical network system comprising: a data service hub for processingupstream radio-frequency analog and generating downstreamradio-frequency analog video service control signals according to afirst timing scheme, the data service hub comprising adata-to-radio-frequency converter for receiving upstream digital datasignals comprising a time stamp that preserves the first timing schemeand that initiates recovery of the upstream radio-frequency analog videoservice control signals by the converter from the upstream digital datasignals; a subscriber optical interface for receiving electricalupstream radio-frequency analog video service control signals, forconverting the electrical upstream radio-frequency analog signals tofirst digital packets and combining the first packets with secondpackets in a time domain for upstream transmission towards the dataservice hub, for preserving the first timing scheme between the upstreamand downstream video service control signals, the subscriber opticalinterface comprising an optical transmitter for converting the first andsecond packets into the optical domain, the subscriber optical interfacefurther comprising an analog-to-digital converter for converting theupstream radio-frequency analog video service control signals intodigital data signals prior to first packet formation and for adding thetime stamp to the digital data signals that preserves the first timingscheme of the video service control signals of the data service hub; andone or more optical waveguides connected to the subscriber opticalinterface for carrying the upstream optical signals and downstreamoptical signals that are propagated according to a second timing schemeindependent of the first timing scheme.
 46. The return path of claim 45,wherein the data service hub comprises an RF return device forcontrolling a timing of RF return signals generated by a plurality ofsubscribers.
 47. The return path of claim 45, wherein the opticaltransmitter comprises an analog laser.
 48. The return path of claim 45,wherein the optical transmitter comprises a Fabry-Perot laser.
 49. Thereturn path of claim 45, wherein the optical transmitter comprises an RFpresence detector for controlling the optical transmitter.
 50. A methodfor returning signals from subscribers to a data service hub in anoptical network system comprising: generating downstream radio-frequencyanalog video service control signals and receiving upstreamradio-frequency analog video service control signals according to afirst timing scheme; receiving electrical upstream radio-frequencyanalog video service control signals at a subscriber optical interface;converting the upstream radio-frequency analog video service controlsignals to a plurality of first digital information packets; receiving aplurality of second digital information packets; preserving the firsttiming scheme between the upstream and downstream video service controlsignals by transmitting both sets of information packets by insertingthe first digital information packets between the second digitalinformation packets in a time domain; converting the first and seconddigital information packets into optical signals; transmitting theoptical signals to the data service hub according to a second timingscheme independent of the first timing scheme; detecting a time stamp inthe first digital information packets with a data-to-radio-frequencyconverter of the data service hub; and initiating recovery of theupstream radio-frequency analog video service control signals from thefirst digital information packets with the data-to-radio-frequencyconverter in response to detecting the time stamp.
 51. The method ofclaim 50, further comprising controlling the timing scheme of theupstream radio-frequency analog video service control signals with thedata service hub.
 52. The method of claim 50, wherein converting thefirst and second digital information packets into optical signalsfurther comprises modulating an optical transmitter with the first andsecond digital information packets.
 53. The method of claim 48, furthercomprising detecting a presence of upstream radio-frequency analog videoservice control signals at the subscriber optical interface.